1. Liberally butter four 4-ounce ramekins or custard cups. Sprinkle a few spoonfuls of the additional sugar inside, tilt the dish to spread the sugar and coat the bottom and sides, then tip out any excess. Set the ramekins on a baking sheet.
2. Preheat the oven to 400ºF (200ºC).
3. Use a whisk, or an electric mixer with the paddle attachment, to mash the cream cheese, egg yolks, goat cheese and lemon zest until the mixture completely smooth.
4. With an electric mixer, or by hand, whisk the egg whites in a clean, dry bowl (not plastic) until frothy, with the salt. Increase the speed, until the whites begin to mound and hold their shape. While whipping, gradually add the sugar, one tablespoon at a time. Once you’ve added all the sugar, beat until stiff.
5. Fold one-third of the beaten egg whites into the goat cheese mixture, then fold in the remaining egg whites just until incorporated. It’s okay to have some tiny bits of white; that’s preferable to overfolding the batter.
6. Scrape the batter into the prepared baking dishes, gently smooth the tops, and sprinkle the soufflés with an even layer of sugar, about 1/2 teaspoon each.
7. Bake the soufflés on the middle rack (or slightly higher, if possible) of the oven for 10 to 15 minutes, until the top is browned and the soufflé is just set but still very jiggly in the center if you nudge it. Depending on your oven, it may take slightly less or more time. Soufflés are best when slightly runny in the center.