Preheat oven to 350 F. Toss the apples with lemon juice in a medium bowl. Heat a large frying pan over medium-high heat and melt the butter until it stops foaming and turns light brown. Stir in the apples, 1/4 C of the sugar, vanilla, cinnamon, & nutmeg. Spread the apples in a single layer and cook without stirring for a couple of minutes, then reduce heat to medium and toss the apples around in the pan until golden brown, about 5-7 minutes. Remove from pan and set aside to cool. Once cooled, spread the apples evenly into a pre-baked gluten-free pie shell (check out the Bob’s Red Mill Gluten-Free Pie Crust Mix that’s on sale!). Next, make the almond topping by gently beating the egg whites until light and foamy, then whisking in the remaining 2 T of sugar, then gently stirring in the sliced almonds. Spread this topping over the apples. Place pie on a sheet pan and bake for 30 minutes, or until golden brown.