Preheat oven to 425°F. Generously butter four 6-ounce ramekins, dust with flour and place on a baking sheet.
Place butter and dulce de leche in a medium saucepan over medium heat and cook, whisking, until melted and combined. Whisk in powdered sugar and salt.
Add eggs, egg yolks and vanilla and whisk to combine. Mix in flour.
Divide batter across prepared ramekins and smooth tops. Bake for 15-18 minutes, or until tops are golden brown and edges are firm, but center still wobbles.
Let cool 2 minutes, then run a knife around the edge of the ramekin and carefully invert onto a plate. Dust with powdered sugar and serve.