Preheat oven to 375 degrees. Toast almonds on a rimmed baking sheet in oven, stirring occasionally, until fragrant and golden brown, about 10 minutes. Let cool completely. Finely grind almonds in a food processor; transfer to a medium bowl. Whisk in flour, 3/4 cup sugar, the baking powder, 3/4 teaspoon salt, and the nutmeg; set aside.Advertisement
Brush a 10-inch cast iron skillet with 2 tablespoons butter. Whisk together remaining 4 tablespoons butter, the milk, egg, and liqueur in a medium bowl. Stir butter mixture into flour mixture. Spread batter evenly into buttered skillet.
Stir together apricots, remaining 1/4 cup plus 2 tablespoons sugar, a pinch of salt, and the lemon juice in a medium bowl. Spread apricot mixture evenly over batter. Bake until a cake tester inserted into center comes out with moist crumbs, 50 minutes to 1 hour. Let cool in skillet on a wire rack 1 hour before serving.