- 1 cup sweetened flaked coconut
- 1 stick unsalted butter, softened
- 1 1/4 cups granulated sugar
- 1 tablespoon grated Key lime zest
- 2 large eggs
- 1 3/4 cups self-rising flour
- 3/4 cup whole milk
- 1/4 cup fresh Key lime juice, divided
- 1 cup confectioners sugar
- 1 tablespoon rum (optional)
- Preheat oven to 350°F with rack in middle. Generously butter a 9- by 2-inch round cake pan and line bottom with a round of parchment paper.
- Toast coconut in a small baking pan in oven, stirring once or twice, until golden, 8 to 12 minutes. Cool. Leave oven on.
- Beat together butter, granulated sugar, and zest with an electric mixer until fluffy. Beat in eggs 1 at a time. Stir together flour and 1/2 cup coconut (reserve remainder for topping). Stir together milk and 2 tablespoons lime juice. At low speed, mix flour and milk mixtures into egg mixture alternately in batches, beginning and ending with flour.
- Spoon batter into pan and smooth top. Bake until golden and a wooden pick inserted into center comes out clean, 40 to 45 minutes. Cool to warm, then turn out of pan and discard parchment.
- Whisk together confectioners sugar, remaining 2 tablespoons lime juice, and rum (if using) and pour over cake. Sprinkle with remaining coconut.