Cut the cabbage into quarters and remove the core.
Place cut side down on a cutting board and cut into 1/4 inch-thick slices.
Core and seed the peppers, slicing into 1/4 inch-thick strips.
In a large skillet heat the butter.
Saute the cabbage, peppers, and onion just until the vegetables begin to wilt.
Add the stock, water, garlic, and pepper flakes.
Simmer briefly, just until the vegetables are tender but still crisp.