Preheat the oven to 400 degrees F (200 degrees C).

Brush butter on the bottom and up the sides of two 5 1/2-ounce ramekins. Scoop in some sugar; rotate ramekins to coat while pouring most of the sugar back into its container. Place ramekins on a shallow baking pan.

Separate eggs between 2 bowls. Add sugar, flour, 1/4 teaspoon salt, vanilla extract, lemon zest, cream cheese, and Cheddar cheese to the yolks. Mix the souffle base with a spatula until sugar and flour disappear.

Sprinkle a pinch of salt over the room-temperature egg whites. Beat with a whisk until soft peaks form; peaks should hold their shape but not be stiff or dry. Stir and fold 1/2 of the egg whites into the souffle base until combined. Gently fold the rest of the egg whites into the batter.

Fill ramekins up to the lip with the batter.

Bake in the preheated oven until puffed and browned, about 12 minutes. Serve immediately.