Key lime pie is a baked custard pie with four ingredients in the filling — sweetened condensed milk, key lime juice, lime zest, and egg yolks — poured into a buttery graham cracker crust. The filling sets firm in the oven in about 15 minutes, then the pie chills until sliceable. It’s worth making because the ingredient list is short, the technique is straightforward, and the result is genuinely tart and creamy in a way that store-bought versions rarely are.
Before you start
Two things determine whether this pie works. First, press the crust firmly and evenly — use the flat bottom of a measuring cup to compact it against the pan sides and base. A loosely packed crust crumbles when you slice. Second, whisk the filling until it’s completely smooth before pouring; any streaks of unmixed yolk will show up as yellow patches in the finished slice. You don’t need a mixer — a balloon whisk and about 90 seconds of steady whisking is all it takes. Also worth noting: the filling should still have a slight wobble at the center when you pull it from the oven. It firms up during chilling, and overbaking makes it rubbery.
Make-ahead notes
This pie is genuinely better made the day before you need it. Two hours of refrigeration is the minimum for the filling to set, but overnight chilling gives you cleaner slices and a more settled flavor. Covered tightly with plastic wrap, it keeps well in the fridge for up to four days. For longer storage, freeze the fully baked and chilled pie — wrap it in plastic, then foil — for up to one month. Thaw overnight in the refrigerator, not at room temperature. Skip the garnish — not worth the extra dish — the pie holds and serves cleanly on its own.
Common problems and fixes
- Crust slides down the sides of the pan during baking: The butter ratio was off or the crust wasn’t pressed firmly enough into the corners. Next time, chill the pressed crust for 10 minutes before baking — it helps it hold its shape.
- Filling is runny after chilling: The pie likely needed more oven time. The center should jiggle like set gelatin, not like liquid, when you remove it. Return a still-runny pie to a 325°F oven for 5–8 more minutes, then re-chill.
- Filling tastes flat or not tart enough: Bottled key lime juice varies widely in acidity and freshness. If you’re using bottled juice, taste it before mixing — if it seems weak, add an extra teaspoon of fresh regular lime juice to sharpen it.
- Filling has a grainy or curdled texture: This usually means the egg yolks were added to warm condensed milk, or the pie was baked at too high a temperature. Mix everything at room temperature and verify your oven isn’t running hot with an inexpensive oven thermometer.
- Slices fall apart when served: The pie wasn’t chilled long enough, or the crust was underbaked. Make sure the crust is lightly browned and smells toasty before you add the filling, and always chill the finished pie for a full two hours minimum before cutting.
Key Lime Pie
Equipment
- 1 9-inch pie pan
- 1 Mixing Bowls
- 1 Whisk
- 1 Measuring cups and spoons
- 1 Oven
- 1 Zester
Ingredients
Graham Cracker Crust
- 1 ½ cups graham cracker crumbs preferably organic
- ⅓ cup granulated sugar
- 6 tablespoons unsalted butter melted
Filling
- 1 cup sweetened condensed milk use high-quality brand for best flavor
- ½ cup key lime juice freshly squeezed is ideal
- 1 tablespoon lime zest
- 4 large egg yolks
Instructions
- Preheat your oven to 350°F (175°C).In a mixing bowl, combine 1 and 1/2 cups of graham cracker crumbs, 1/3 cup granulated sugar, and 6 tablespoons melted unsalted butter. Mix until the crumbs are evenly coated with butter.
- Press the mixture firmly into the bottom and sides of a 9-inch pie pan, creating an even layer. Bake for 10 minutes or until lightly browned and fragrant.
- In another bowl, whisk together 1 cup of sweetened condensed milk, 1/2 cup key lime juice, 1 tablespoon lime zest, and 4 egg yolks until smooth and well combined.
- Pour the filling mixture into the pre-baked crust, spreading it evenly. Bake for an additional 15 minutes, or until the center is set but still slightly jiggly.
- Allow the pie to cool at room temperature, then refrigerate for at least 2 hours before serving to fully set the filling.
Notes
Tammy’s Tips
- For a more vibrant flavor, consider adding a few drops of pure vanilla extract to the filling.
- If you cannot find fresh key limes, regular limes will suffice, though the flavor will be slightly less intense.
- For a dietary-friendly version, use gluten-free graham crackers and substitute coconut milk for those with lactose intolerance.
Nutrition
Your questions, answered
Can I use regular limes instead of key limes?
Yes, regular Persian limes work and the pie will still taste good. The flavor will be a little less floral and slightly less tart than key limes, but most people won’t notice the difference unless they’re comparing the two side by side.
Do I really need to bake the filling, or can I just refrigerate it?
Bake it. The raw egg yolks in an unbaked filling are a food safety concern, and baking also gives the custard a firmer, more sliceable texture. Fifteen minutes at 350°F is all it takes.
How do I know when the filling is actually set and ready to come out of the oven?
Give the pan a gentle nudge — the edges should be fully set and the center should wobble slightly, like firm Jell-O, not ripple like liquid. It will continue to firm up as it cools and chills, so pulling it at this stage is correct.
What to bake next
- Tropical Lime Bars with Toasted Coconut Crunch
- Southern-Style Lemon Pie with Creamy Condensed Milk Filling
- Tropical Bliss Toasted Coconut Custard Pie
- Mediterranean Sunshine Lemon Crumble Bars