Heat oven to 130°, oven rack to bottom third of oven, this is going to rise. Butter and sugar – like your were using flour, but use sugar to coat the sides of the dishes instead-- one or two tall-sided oven dishes, I use 1 soufflé dish and one bread pan usually.
Be sure your egg white beating bowls are completely grease free and dry. Separate your eggs carefully, one by one into a separate bowl is best, you must not have even the tiniest bit of yellow in your whites or the whole recipe won't work.
Start beating the egg whites at a moderate speed until foamy, beat in the lemon juice and salt and gradually increase speed to fast, you really need an electric beater for this. When the egg white form soft peak, very gradually add the sugar in small amounts, then beat at high for a few minutes til you get stiff peaks. Beat in the vanilla. Scoop the mixture into the prepared dish or dishes, you want them about filled, just use a second dish if you have too much. I sometimes use a prepared bread pan for the excess and slide it onto the same oven rack as the soufflé dish.
Bake immediately in the preheated oven 35-40 minutes. It will rise and turn golden. A bit too much time is better than too little. Remove and cool at room temperature, it will sink a bit. When cool, cover and refrigerate. May be made up to a couple days in advance and even frozen.
Cut into 6 wedges and serve on a pool of cool crème anglaise, which is actually a bit difficult to make at home. If you have any hesitation, buy it pre-made. If you are feeling adventurous, use your leftover egg yolks and any crème anglaise recipe from the web and follow the directions EXACTLY-- it must NEVER boil.