Preheat oven to 325 F
Cut a piece of parchment paper to nestle in bottom of 8 in round pan. Spray with cooking spray
Whisk together dry ingredients in small bowl (almond and coconut flours, baking powder, and salt).
Cream butter, vanilla, and sugar. Add one egg and blend until fluffy
Add ricotta, lemon juice, and lemon zest, beating thoroughly until combined
Add about a third of dry mix and one egg to wet mixture and blend. Continue until used all 3 remaining eggs and dry ingredients
Spread batter in 8 " pan and smooth out top with spatula as best you can.
Bake for 45-50 minutes until toothpick comes out clean
It will not look brown on top of the cake when it is done! So, don't look for that, use the toothpick method.
Let cool for 15 minutes and then remove by using a knife around edges to loosen.
You can leave on the counter covered in plastic wrap for 2-3 days, but then will need to refrigerate. If it is super hot where you are, just put in fridge right away!