If you’re going to bake the rounds as individual layers, a nice little trick is to bake the cake with the carmel layer already in the pan. You’ll need to prep the pans as per usual and cut the parchment rounds to be EXACTLY the size of the pan bottom (or plan on having a tough cleaning project to remove the carmel!). For each of three pans, use 230 gms BUTTER, 1/4 tsp salt, 1 cup firmly packet brown sugar and 1/4 cup heavy cream. Beat room temp butter for about 5 minutes with the paddle in a KA-type mixer until fluffy, then cream the brown sugar and salt into it for ~ 4 or 5 more minutes, adding the heavy cream during the last 2 minutes of mixing. Spread the mixture evenly over the bottom of your papered, greased and floured pans, then refrigerate them while you make the first batch of yellow cake batter. Pour the batter over the chilled mixtur in the pans and bake as usual, adding about 3 minutes to your normal baking time. This is really good, and can be supplemented by adding coarsely chopped pecans or walnuts to the carmel layer before the batter. Amazingly enough, this layer of nuts will stay free of batter after baking and have the best carmel layer over them in the top of the round. They are so attractive after baking I have served them several times without frosting. If you do full-sized rounds, they are really nice with a custard filling and fruit between layers. I like banana cake with a vanilla custard and sliced raw bananas between rounds.
I would suggest that if you do the individually baked thin layers rather than torting a frozen pound cake, that you freeze the rounds about 30 minutes just prior to assembly of the finished cake to make handling the thin rounds much easier. Lots of good carmel buttercream frostings out there, make sure to use a serrated knife to slice/saw the cake when serving to avoid pushing the frosting/filling out of the assembled cake.
HTH