Apple-almond browned butter cake

1-1/2 cups (3/4 lb.) salted Challenge European Style Butter
1-3/4 cups slivered almonds
3 cups powdered sugar
about 1-1/2 cups all-purpose flour
8 large egg whites (1-1/8 cups)
1 tablespoon grated lemon peel
1 tablespoon grated orange peel
1-3/4 cups finely chopped peeled Golden Delicious apples
vanilla ice cream
warm caramel sauce

In a 12-inch frying pan or 5- to 6-quart pan over high heat, melt 1-1/2 cups butter. Stir often until the milk-solid particles turn golden brown, 5-7 minutes. Remove at once from heat; let stand until warm, 15 to 20 minutes (or next pan in cold water and stir often, 5 to 8 minutes). Meanwhile, in a food processor, whirl 3/4 cup slivered almonds to a fine powder (or finely grate with a nut grater); scrape into a large bowl. Spread remaining 1 cup slivered almonds in a 10- by 15-inch pan. Bake in a 350 F oven until almonds are golden brown, 6 to 12 minutes. Let cool slightly, then coarsely chop. To the bowl containing ground almonds, add toasted almonds, sugar, and 1-1/4 cups flour. Stir to mix well. Scrape melted butter with all browned particles into bowl; mix. Add egg whites, lemon peel, and orange peel. Beat with a mixer on medium speed, scraping bowl often, until batter is well blended. Add chopped apples and stir to mix. Butter and flour a 9-inch cheesecake pan with removable rim. Scrape batter into pan. Bake in a 325 F oven until cake is golden brown, firm in the center when lightly pressed, and begins to pull from pan sides, 1 hour to 1 hour and 10 minutes. Let cake stand in pan on a rack at least 20 minutes or until cool, about 1 hour. Slide a thin-bladed knife between warm or cool cake and pan rim; remove rim. Set cake on a rimmed plate and, if desired, pour about 1/2 cup warm caramel sauce over the top. Cut into wedges; serve with scoops of ice cream and remaining caramel sauce to add to taste.
Warm Caramel Sauce:
In a 3- to 4-quart pan over high heat, stir 3 tablespoons salted Challenge European Style Butter and 2/3 cup sugar until mixture is caramel-colored, 2 to 4 minutes. Remove from heat and add 2/3 cup whipping cream; stir until blended (mixture foams). Return to high heat; stir until caramel sauce comes to a rolling boil, 1 to 2 minutes. Serve hot. Makes 1 cup.