A light and delicious pound cake that's great served plain, or with options like berries, ice cream, toasted with jam, dipped in melted chocolate chips, or dunked in coffee. Also perfect for cutting into cubes to make trifle.
Preheat oven to 325 degrees. Coat a 9- or 10-inch tube pan with cooking or baking spray.
In a large mixing bowl, beat butter and sugar on medium until well blended, about five minutes. Gradually add egg whites/egg mixture, beating well. (If using 7 egg whites, add them one at a time, beating after each addition.)
In a small bowl, whisk sour cream and baking soda together. Measure the flour by lightly spooning it into dry measuring cups and leveling them off with a knife. Keep the flour in a bowl until you are ready to sift. Sift the flour by gradually adding it to a fine-mesh strainer placed over a medium bowl. Combine the sifted flour with salt.
Add some of the flour mixture to the butter/sugar mixture, beat, then add some of the sour cream mixture and beat. Continue alternating the flour and sour cream, beating until the batter is mixed, beginning and ending with the flour. Stir in the vanilla and almond extracts (or use all vanilla).
Pour the batter into the greased pan and sharply tap the pan on the counter once to remove air bubbles. Bake at 325 degrees for 1 hour and 20 minutes. Check for doneness by inserting a toothpick or cake tester into the center. If it comes out clean with a couple of crumbs, it is done just enough for a soft top crust. If you prefer a firmer top crust, bake for up to 15 minutes longer.
Cool the cake for 10 minutes in the pan on a wire rack. Then remove the cake from the pan by placing a dinner plate over the top and inverting the cake onto the plate. (The cake will be upside down at this point.) Place a wire rack over the cake and invert again, so that the cake is resting right side up on the wire rack. Cool completely before slicing. (Cake tastes best when completely cooled.)
Using store-bought egg whites without additives is a great time saver and prevents being stuck with leftover yolks. Look for them in cartons in the dairy aisle.