Preheat oven to 425°. Grease six 6-oz. ramekins with butter.
Warm white chocolate and the chopped butter in a small saucepan over low heat, stirring constantly, until melted, about 5 minutes. Scrape into a large bowl.
Stir in flour, granulated sugar, and salt until smooth. Whisk in eggs, egg yolks, lemon zest, lemon juice, lemon curd, and vanilla.
Pour batter into prepared ramekins and set ramekins on a rimmed baking sheet. Bake until edges are golden brown and center is just beginning to set (it should still look a little soft), 12 to 14 minutes. On each cake, run a knife around edge to loosen and carefully flip ramekin onto a dessert plate. Let stand for a minute or two, then lift off ramekin, easing cake onto plate with a small spatula if needed.
Dust cakes with powdered sugar and serve warm with strawberries.