While onion and rice cook, core, seed and thinly slice poblano. Finely mince garlic. Once onion is softened, add poblano to pan. Cook, tossing occasionally, until poblano is tender, 5-7 minutes. Toss in half the garlic and cook one minute more. Pour in ¼ cup water and let simmer until just evaporated, 1-2 minutes. Season with salt and pepper.