Preparation Method
- Preheat the oven to 350°F (180°C) with a rack set in the middle position. Grease a 13-by-9-inch (33-by-23-centimeter) baking pan. Set aside.
- Make the crust: In the mixing bowl of the stand mixer fitted with the flat beater attachment, beat butter, granulated sugar, zest, and salt on medium (5–6) speed until blended, about 1 minute. Reduce the mixer speed to low (1–2), scraping down the bowl as needed. Gradually add flour until crumbs form, about 1 minute. Press the flour mixture firmly into the bottom of the prepared baking pan.
- Bake until the edges are golden brown, 18–20 minutes.
- Make the filling: Clean and dry the mixing bowl. In the mixing bowl of the stand mixer fitted with the whisk attachment, beat eggs, granulated sugar, Key lime juice, and zest on low speed (1–2) until just blended, about 2 minutes.
- In a small bowl, whisk together flour and baking powder. Gradually beat the flour mixture into the egg mixture until smooth. Immediately pour the mixture over the hot crust.
- Bake until the mixture is set, 20–22 minutes. (The filling may crack during baking or cooling.)
- Let cool completely in the pan on a wire rack. Sprinkle with confectioners’ sugar and cut into squares.
Pro Tip
If you are unable to find Key limes, substitute equal parts lemon and lime juice.
