If the cherries are fresh, pit them and let them dry on a paper towel. If they are frozen, let them thaw and remove the extra liquid. Sift some coconut or tapioca flour on them.
Mix all the flours, and salt in a bowl (you can sift them after you mix them).
Separate the egg yolks from the egg white into two mixing bowls. Add the sweetener, lemon zest and vanilla to the egg yolks, and mix with an electric mixer until they reach a creamy consistency. Add the oil and mix again to incorporate the oil.
Beat the egg whites with the electric mixer until they become stiff.
Gently fold the egg whites with the spatula, gradually adding them to the egg yolks. Gradually add the sifted flour into the mixture and fold with a spatula, without overmixing, until all the flour gets incorporated.
Transfer the batter to the baking dish, level it, and place the cherries on top, lightly pressing them down.
In a preheated oven at 350 F/180 C, bake for 25 minutes, until golden brown on top (a toothpick inserted in the middle should come out clean).
Remove from the oven and let it cool for about 30 minutes before you transfer it to a cutting board and slice it into squares. Dust with inulin powder and serve.