This cheesy rice casserole is a particular favorite in our house. The grassy poblano peppers are the ones used to make chile rellenos, the traditional cheese-stuffed peppers that are fried and served with a silky tomato sauce. I’ve captured all those flavors in this easy-to-make baked dish reminiscent of ones my grandma would make when I was growing up—which means I’m one step closer to fulfilling my lifelong goal of becoming my grandmother.
Preheat the oven to 425°F (220°C). Char the poblanos over a gas flame or under the broiler. Turn every couple of minutes to evenly char on all sides. Place in a heatproof bowl and cover with plastic wrap. Let sit until cool enough to handle. Peel off the charred skin and rinse under cold water. Remove the stems and seeds, and chop into large pieces.
Heat the butter in a small 4-6 quart, oven-safe Dutch oven with a lid over medium heat. Once the butter is melted and foaming, add the onion and garlic. Season with salt and pepper. Cook until tender. Add the rice and stir frequently, until the rice is opaque and golden. Add the poblanos, tomatoes, oregano, Oaxaca cheese, water, salt and a pinch or two more of pepper.
Stir to combine. Cover and bake until the rice is cooked, about 30 minutes. Uncover and bake 10 minutes more, or until the top is golden and bubbly.