Preheat oven to 425 and line two baking sheets with tin foil.
Trim the cabbage bottom, so cabbage rests flat. Holding the cabbage firmly, carve a circle out of the top of the cabbage (just as you would carve a pumpkin). Remove "top" of cabbage and set aside.
Drizzle cabbage "top" and "bottom" with 1 Tbsp olive oil and rub the olive all over the cabbage. Sprinkle with garlic salt and pepper.
Toss beet slices with remaining 1 Tbsp olive oil, garlic, garlic salt and pepper.
Place cabbage "top" and "bottom" on one baking sheet and beets on the other and place into oven.
After 15 minutes, flip beet slices and flip cabbage and roast another 15 minutes. Remove beets from oven and set aside. Flip cabbage again and roast an additional 15 minutes, or until outer cabbage leaves begin to crisp and the full cabbage is tender. Cooking time may vary, depending on size of cabbage.
Once tender, remove cabbage from oven. Reserve "top" of cabbage for another use (perhaps part of tomorrow's lunch?). Place cabbage carved side up on a serving dish. Fill with golden beet coins.
Serve.