Certainly on the pie side of cake.
It’s called “cake pie” because a cake-like layer forms on top of the custard-like layer when you bake it. There are references going back as far as the 1910s, but they’re pay-per-view; here’s a mention from the April 23, 1936 edition of the Middlesboro (Kentucky) Daily News.
From the box of D.W. from Cedar Falls, Iowa.
Lemon Cake Pie
5 T. flour
Salt
1 c. sugar
2 egg yolks
2 T. melted butter
Grated rind of 1 lemon
Beat 3 minutes and add 1 c. milk, and fold in egg whites which have been beaten stiff. Bake in unbaked shell, 350 deg. for 40 min.
Donna [G?]