Add the strawberries, sugar, lemon juice, and salt to a blender or food processor. Blend until completely smooth.

Add the purée to a small saucepan. Simmer on medium-low heat until the purée is reduced by half, stirring occasionally. It'll take about 20-30 minutes to reduce. Cool to room temperature before making the cake.

Preheat the oven to 350°F and spray 3 (8-inch) round cake pans with gluten-free nonstick cooking spray and line the bottoms with parchment paper.

In a large bowl, whisk together the gluten-free flour, cornstarch, xanthan gum, salt, baking powder, baking soda, and granulated sugar. Set aside.

In a medium bowl, whisk together the egg yolks, buttermilk, melted butter, oil, vanilla extract, concentrated strawberry purée, and food coloring (if using). Set aside.

Add the egg whites and cream of tartar to a separate, clean mixing bowl. Beat with an electric mixer on medium-low speed until the egg whites hold a stiff peak. Then set the egg whites aside.

Pour the wet ingredients into the dry ingredients and mix until just incorporated. Add half of the whipped egg whites to the batter and gently fold in with a spoon. When it's mostly folded in, add the remaining egg whites. Gently fold in until no white streaks remain. Make sure you're folding and not stirring/mixing so you don't deflate the egg whites. It may take a minute or two to fully incorporate.

Transfer the batter to the prepared pans, making sure it's distributed evenly and spread the batter in the pans. Bake for 20-24 minutes.

Cool the cakes in the pan for 25 minutes then remove them from the pans and cool completely on wire racks. Once the cakes are cooled, frost them with the strawberry cream cheese frosting.

Add the freeze-dried strawberries to a plastic bag and crush them with a rolling pin or mallet until they're a fine powder. Set aside.

Add the cream cheese and butter to the bowl of a stand mixer fitted with the paddle attachment. Beat together until smooth, about 1 minute.

Add the powdered sugar and mix on the lowest speed until the sugar is incorporated, scraping down the bowl as needed. Add the freeze-dried strawberry powder, strawberry concentrate, and vanilla extract.

Mix an additional 30 seconds to 1 minute, until the frosting is smooth and creamy.

Use immediately or store, covered, in the refrigerator until ready to use. If you refrigerate the frosting, let it come to room temperature and mix well before using.