How can I achieve even browning on the bottom of baked buns? I've taken to using my go-to Honey-Oat Pain de Mie recipe to make sandwich buns. I just separate the dough after the first rising into eight dough balls on a sheet pan. As a loaf, I always make this bread in a Pullman pan, so the crust isn't an issue. As buns, this dough browns quite a bit (not surprising considering all the honey) which would be fine if it browned evenly. Unfortunately, the bottom of the buns (in contact with the pan) don't brown at all. In contrast to the toasty tops, that isn't a nice effect. I've tried flipping the buns halfway through baking, and that helps a bit, but the bottoms of the buns never get as brown as the tops. If I flip sooner, I end up up with even browning, but flattened buns. Can anyone help?
You may wish to try a dark colored baking sheet, such as this one from Chicago Metallic (not an endorsement, I haven't tried it.)



The dark finish will help absorb radiant heat, which is a major mode in baking, and better brown the bottoms.  In fact, such a tray probably would bake too fast for the bottoms of cookies.

Buttering it will also help conduct heat from the pan to the bottom crust, although you will also get a touch of that almost-fried texture (I like it, but it might not be what you have in mind).