if you want to lighten up your cheesecake, instead of the baking powder or soda, try these:
- beat your cream cheese in your kitchenaid or with a mixer. having it at room temperature from the beginning will help. you can probably mix it for at least 10 or 15 minute. the consistency can get to nearly marshmallow-fluff-like.
- separate your eggs. you can beat the yolks with some of the sugar (2 1/2 c sounds like too much for just 5 yolks though) over hot water (or directly over the flame if you're careful) until it increases about 3 or 4 times in volume. it'll be a very pale yellow and will come off of a wooden spoon in a fairly wide ribbon, taking a few seconds to settle.
- whip your whites till they form soft peaks, not stiff. if you beat them till they're stiff, the bubbles will expand & burst when cooked, deflating the cake.
- sift your flour 3 times
put your cake together the way you would a geniose, alternately folding in the ingredients. i've never tried whipping up sour cream or ricotta. you might add it to the cream cheese after it's fluffy and whip it some more. or try whipping them separately. or not at all and just fold them into the whipped cream cheese. the lemon juice and vanilla you might want to add directly to the cream cheese when whipping. it'll be even softer and you won't have to fold them in separately later and loose a little volume.