Ingredients
1 1/2 cups graham cracker crumbs (from 12 crackers)
1 cup (2 sticks) unsalted butter, room temperature, plus 5 tablespoons melted
1 1/4 cups plus 2 tablespoons granulated sugar
1 1/4 teaspoons coarse salt
1 1/2 cups all-purpose flour, plus 2 tablespoons
1 1/2 teaspoons baking powder
4 large eggs, room temperature
1/2 teaspoon pure vanilla extract
3 tablespoons freshly grated key lime zest (from 12 key limes), plus more for topping
6 tablespoons sour cream, room temperature
Key Lime Frosting
Preparation
Preheat oven to 350 degrees. Line two standard 12-cup muffin tins with paper liners. In a food processor, pulse together graham cracker crumbs, 5 tablespoons melted butter, 1/4 cup sugar and 1/4 teaspoon salt until mixture holds together when squeezed. Spoon 1 to 2 tablespoons crumb mixture into each liner and press firmly using the bottom of a lightly oiled shot glass or small bowl. Bake until set, 5 to 7 minutes; cool completely. Reduce oven to 325 degrees.
In a medium bowl, whisk together flour, baking powder, and remaining 1 teaspoon salt. Using an electric mixer, beat together remaining 1 cup butter and 1 cup plus 2 tablespoons sugar on medium-high speed until pale and fluffy, at least 8 minutes. Add eggs, one at a time, beating thoroughly between each addition, and scraping down sides of bowl as needed. Beat in vanilla and zest. Reduce speed to low; add flour mixture in 2 batches, alternating with sour cream and beating until just incorporated.
Divide batter among cups, filling each about three-quarters full; tap pans on countertop once to evenly distribute batter. Bake until a cake tester inserted in centers comes out clean, about 26 minutes. Transfer tins to wire racks to cool 10 minutes; turn out cupcakes onto racks and let cool completely, about 30 minutes. Frost with 2 heaping tablespoons key lime frosting; top with lime zest.
