How to "fill" a cake made from a cupcake recipe

I have several cupcake recipes. I know it's easy to convert to a cake (just adjust baking time and figure out correct pan size). My question is many of the cupcake recipes have a filling that is (for the most part) just sort of stabbed into the baked cupcake using a squeeze bottle. These fillings are usually between artificial maple syrup and pudding in consistency/thickness. If I want to use the filling, how would I incorporate it into the cake other than repeatedly "stabbing" the cake in various places? A google search only tells me to tort the cake, but I'd like to leave it in a single layer if possible (plus I don't think the cupcake fillings would hold up to be filling layer in a layered cake).