In the work bowl of a food processor, pulse fresh strawberries until nearly smooth but a few small pieces remain. Transfer to a small saucepan; bring strawberry purée to a boil over medium-high heat. Reduce heat to medium-low, and cook, stirring frequently, until thickened and reduced to ? cup, 10 to 15 minutes. Remove from heat, and let cool completely.
Preheat oven to 350°F (180°C). Spray a 6-cup Nordic Ware Charlotte Cake Pan with baking spray with flour.
In a medium bowl, whisk together all-purpose flour, baking powder, kosher salt, and baking soda.
In a large bowl, whisk together granulated sugar, vegetable oil, and egg whites. Whisk in whole milk, fresh lemon juice, and vanilla extract.
Add flour mixture to wet ingredients, and whisk until almost combined. Gently fold in strawberry purée and red gel food coloring (if using) just until combined.
Spread batter into prepared pan. Firmly tap pan on kitchen towel-lined counter to settle batter.
Bake until cake springs back when lightly touched in center and a wooden pick inserted in center comes out clean, 20 to 25 minutes. Let cool in pan on a wire rack for 10 minutes.
Invert cake onto a wire rack, and let cool completely.
Spread Vanilla Bean Custard into center of cooled cake. Refrigerate until custard is set, about 1 hour.
Just before serving, sprinkle remaining granulated sugar onto custard, leaving a ¼-inch border around edges of custard. Using a handheld kitchen torch, carefully brown sugar. Serve immediately.
