I agree with Kathy1, it’s a very cute pan.
Iíve baked recipes that are intended for loaf and bundt pans successfully in the Wilton pan, which has a 10-cup capacity. You donít want any more than 7 cups of batter, ~4 for the base and ~3 for the top. Recipes intended for 10-12 cup bundt pans usually produce enough batter; I double recipes intended for a loaf pan.
I usually bake the batter in the cupcake base for a few minutes (10-15min if the total baking time for the recipe is 45-60min respectively) before adding the batter to the top. It works but you do have to work very quickly to grease and fill the top.
I cook each side separately so that it cooks evenly.
Kathy1, I’ve never liked removing the partially baked cake from the oven…... I think I’ll try your method next time.