Preheat the oven to 350 F, and position a rack in the center of the oven. Spray the bottoms of three 6-inch round cake pans with non-stick baking spray.
In a saucepan, melt the butter over medium heat. Continue to cook the butter until nutty, golden brown milk solids form at the bottom of the pan. This process might take about 10 minutes. First the butter will hiss and splatter as the water evaporates, then as it quiets down, a layer of foam will form on top of the butter. This means the butter is done. Immediately remove from the heat, and scrape the butter, including the brown milk solids, into a large bowl. Let cool for 10 minutes.
In a bowl, whisk together the cooled brown butter with the granulated sugar, eggs, vanilla extract, almond extract, milk and sour cream, until combined.
In a separate bowl, sift together the flours, salt, baking powder and cardamom. Add the almond flour, then whisk until everything is evenly distributed.
Add the dry ingredients to the wet, whisking just until moistened.
Divide the batter between the prepared pans, and bake for about 25-30 minutes, until the top springs back when gently touched, or a toothpick or cake tester comes out clean. Set the pans on a wire rack, covered with a clean kitchen towel, and cool completely before frosting.
Prick the cakes with a toothpick or cake skewer, then use a pastry brush to brush the Amaretto liqueur over the cakes, letting it soak in before assembling and frosting your cake.