Preparation Preheat oven to 400°F. Brush twelve 1/3-cup muffin cups with 1 tablespoon melted butter. Place almonds and flour in processor and pulse until almonds are finely ground. Beat egg whites in large bowl until frothy. Sift 2 cups sugar over egg whites. Add ground almond mixture and remaining 13 tablespoons melted butter; fold just to blend. Divide batter among muffin cups. Sprinkle tops with lemon peel and lime peel. Bake cakes until golden and centers spring back when touched, about 20 minutes. Cool 5 minutes. Run thin knife around molds and invert cakes onto rack. DO AHEAD Can be made 8 hours ahead. Cool; cover and store at room temperature. Sprinkle tops of cakes with powdered sugar. Serve warm or at room temperature.
Preparation Preheat oven to 400°F. Brush twelve 1/3-cup muffin cups with 1 tablespoon melted butter. Place almonds and flour in processor and pulse until almonds are finely ground. Beat egg whites in large bowl until frothy. Sift 2 cups sugar over egg whites. Add ground almond mixture and remaining 13 tablespoons melted butter; fold just to blend. Divide batter among muffin cups. Sprinkle tops with lemon peel and lime peel. Bake cakes until golden and centers spring back when touched, about 20 minutes. Cool 5 minutes. Run thin knife around molds and invert cakes onto rack. DO AHEAD Can be made 8 hours ahead. Cool; cover and store at room temperature. Sprinkle tops of cakes with powdered sugar. Serve warm or at room temperature.