Here's a very easy, tried and true sponge cake recipe - either two 9 inch round layers or one 13X9 rectangle, or a sheet pan 15 long (don;t remember width) or an angel pan, though it won;t fill it.
If you have a mixer it's so easy
1 cup sugar (superfine is best, but you can use any granulated)
1 cup flour
1 tsp vanilla
1/2 tsp salt
Sponge cakes are without butter (though i believe the british "sponge" is our butter cake)
Beat the whole eggs with salt and vanilla till extremely fluffy and you can't really see the bubbles because it's all foam. Beat in the sugar gradually, while beating at high speed. Keep beating till it's a wonderfully soft and fluffy mass, and when you lift the beater it leaves a trail that slowly dissolves on the surface of the mixture.
Sift the flour over it, and fold in (dip a rubber spatula in the center, push to the bottom and then scrape up along the edge closest to you and dump the egg mixture that you get in the spatula over the flour. Turn 1/8 turn and do the same - into the center and up the edge and over, then anpther 1/8 turn, untill all the dry flour has disappeared. You can stir through it slowly to be sure, but don't beat it once you added the flour.,
Grease and paper line the bottom of the pan only (the grease on the sides supposedly makes the cake not rise as well because it slides down on the greasy sides - but be sure to grease and line the bottom). Bake at 350 until lightly browned and if you touch the top lightly it springs back.
Time depends on the cake size, but start checking at 20 min.
If you don;t have a good electric stand mixer, then separate the eggs and beat the yolks with 3/4 of the sugar, salt and vanilla. In a separate bowl beat the whites till fairly stiff, then add the rest of the sugar a little at a time, like a tsp at a time, as ytou continue to beat. Beat till the whites are very stiff and you can turn the bowl over and they don;t slide out.
Add 1/4 of the whites to the yolks and mix well. Then sift the flour on top of that, and add the whites on top, and do the folding as i described above.
It's no harder than a mix, tastes better and is pretty foolproof.