There’s a reason Key lime pie is legendary. When done right, it delivers an unforgettable burst of bright, tangy flavor contrasted by sweet, creamy richness and a crumbly, buttery crust. This recipe is our gold standard—simple, requiring no special equipment, and engineered for perfect texture every time.
We use the classic, no-fuss filling of just three ingredients that sets into a lush, firm custard, all nestled in a homemade graham crust. The result is a pie that tastes like a vacation: refreshing, indulgent, and utterly satisfying.
The Science of the Set & The Crust
The magic of a true Key lime pie filling lies in a simple chemical reaction: the acid in the lime juice reacts with the proteins in the sweetened condensed milk and egg yolks, causing the mixture to thicken naturally. This is called “souring” or acid-curdling. Baking the pie briefly (or chilling it thoroughly for a no-bake version) firms this reaction into a smooth, sliceable custard.
The intense lime flavor comes from using genuine, aromatic Key lime juice, which is slightly more floral and tart than regular Persian limes. The graham cracker crust provides essential textural contrast. Toasting the crust binds it and deepens its buttery, nutty flavor, creating a sturdy base that won’t get soggy under the creamy filling. This perfect interplay of tart, sweet, creamy, and crunchy is what makes each bite sublime.
Ingredients
For the Graham Cracker Crust:
- 1 ½ cups (150g) graham cracker crumbs (about 12 full sheets)
- ⅓ cup (66g) granulated sugar
- 6 tablespoons (85g) unsalted butter, melted
- Pinch of salt
For the Key Lime Filling:
- 4 large egg yolks
- 2 (14-ounce) cans sweetened condensed milk
- ¾ cup (180ml) freshly squeezed Key lime juice (about 20-25 Key limes, or use bottled Nellie & Joe’s)
- 1 tablespoon grated Key lime zest (optional, for intense flavor)
For the Topping: Whipped cream or meringue.
Instructions
1. The Pressed & Baked Crust: Preheat oven to 350°F (175°C). In a medium bowl, combine the graham cracker crumbs, sugar, and salt. Stir in the melted butter until the mixture resembles wet sand and holds together when pressed. Press firmly and evenly into the bottom and up the sides of a 9-inch pie plate. Bake for 8-10 minutes until fragrant and lightly browned. Set aside to cool slightly. Reduce oven temperature to 325°F (160°C).
2. The Combined Filling Mixture: In a large bowl, whisk the egg yolks until smooth. Whisk in the sweetened condensed milk until fully combined and smooth. Gradually whisk in the Key lime juice and zest (if using) until the mixture is homogenous, thick, and pale yellow.
3. The Filled Pie Shell: Pour the filling into the slightly cooled, pre-baked graham cracker crust. Spread it gently into an even layer, tapping the pan lightly on the counter to remove any air bubbles.
4. The Baked & Set Pie: Bake the pie at 325°F (160°C) for 15-18 minutes. The pie is done when the edges are set but the center still has a slight, gentle jiggle when nudged—it will firm up as it cools. Do not let it brown.
5. The Fully Chilled Pie: Let the pie cool completely on a wire rack for about 1 hour, then refrigerate uncovered for at least 4 hours, or preferably overnight, until completely chilled and firm.
6. The Finished Slice: Just before serving, top with freshly whipped cream. Slice with a clean, sharp knife. Serve cold.
Pro-Tips for Pie Perfection
- Use the Right Juice: For authentic flavor, seek out bottled Key lime juice (Nellie & Joe’s is widely available) or juice fresh Key limes. Regular Persian lime juice works but has a different, sharper profile.
- Don’t Overbake: The filling will continue to set from residual heat. Overbaking can cause cracking or a rubbery texture.
- Chill Thoroughly: This is non-negotiable for clean slices. Overnight chilling yields the best texture and flavor melding.
- Press the Crust Firmly: Use a flat-bottomed cup to press the crumbs firmly and evenly into the plate for a crust that holds together.
- Whipped Cream Wisdom: For the best topping, whip 1 cup of cold heavy cream with 2 tbsp powdered sugar and ½ tsp vanilla to stiff peaks. Pipe or dollop on just before serving.
- Make Ahead: The baked and chilled pie (without topping) can be covered and refrigerated for up to 3 days. Add cream before serving.
This Perfect Key Lime Pie is a celebration of simplicity, delivering pure, sunny flavor in every bite.