Cook the brown rice as directed on the package.
Slice the stem out of the mustard green leaves.
Roll up the leaves together and slice down, so it will cook faster.
In a large skillet, melt the butter, then add the chopped onion and the crushed garlic.
Saute for 3-4 minutes, or until onions begin to turn translucent.
Then add the sliced greens and saute for 2-3 minutes, or until wilted.
Then stir in the black-eyed peas and the diced tomatoes. Let simmer on low for 10-15 minutes.
Serve the Black-eyed Peas and Greens over Brown Rice.