Place the tofu, sugar, gram flour, oil, vanilla and lemon juice into a blender and blend well. Add the soya milk gradually.
Transfer to a large bowl and fold in the flour.
Spoon into a greased 9 inch / 23 centimeter cake tin (the sort with a detachable bases and loosenable side is best) and bake for 45 mins at gas mark 4 / 180C / 350F until golden and firm to the touch. Cool in the tin.
Please note that I have not attempted this recipe so it will almost certainly need tweaking.
According to my cake encyclopedia, angel food cake is a sponge cake with a lot of cornflour in it and hardly any flour. It also contains lots of eggs (10, in my recipe!), a little lemon juice and vanilla.
As the egg content in this cake is so preposterously high, veganising this cake will be difficult. Simply substituting oil for the egg will not work.
If I was going to make it, I would try the above.