Preheat oven to 350. Prepare lasagna pan with parchment lining. If using an angel food cake pan, do not spray anything in the pan.
Sift together 3/4c sugar and cake flour in a bowl, set aside.
Using the whisk attachment for your stand mixer or hand mixer, add your 12 egg whites and beat until foamy, about 2-3 minutes.
Add cream of tartar, lemon juice, vanilla extract and vanilla seeds from scraped bean.
Beat until you see soft peaks.
Once soft peaks form, beat in 3/4c sugar 1 tablespoon at a time until you get stiff peaks and they are glossy.
Slowly sift flour and sugar mixture into egg whites, 1/4 c at a time. Gently fold the flour mixture into the eggs. Repeat until all of the flour sugar mixture has been added to the eggs.
Pour batter into the lasagna sheet or angel food cake. Gently tap the pan on the counter to remove any air bubbles.
Bake for 40-45 minutes until the center is firm. Set aside and allow to cool while making the roasted strawberries.