Step 1: Preheat your oven to 400°F (200°C). Place the poblano peppers on a baking sheet and roast for 20-25 minutes, turning occasionally, until the skin is charred and blistered. Alternatively, you can char them over an open flame on a gas stove.
Step 2: Once charred, immediately transfer the hot peppers to a bowl and cover tightly with plastic wrap or place them in a sealed paper bag. Let them steam for 10-15 minutes. This makes the skin easier to peel.
Step 3: While peppers are steaming, prepare the sauce. Heat 1 tablespoon of olive oil in a medium saucepan over medium heat. Add chopped onion and sauté until softened, about 5 minutes. Add minced garlic and cook for another minute until fragrant.
Step 4: Stir in the crushed tomatoes, broth, cumin, and oregano. Bring to a simmer, then reduce heat to low and let it cook for at least 15 minutes, allowing flavors to meld. Season with salt and pepper to taste.
Step 5: Carefully peel the skin from the cooled poblano peppers. Make a slit lengthwise down one side of each pepper, being careful not to cut all the way through, and gently remove the seeds and membranes. Rinse lightly if needed.
Step 6: In a small bowl, combine the Monterey Jack and cheddar cheeses. Evenly stuff each poblano pepper with the cheese mixture. Close the slit as much as possible.
Step 7: Pour about half of the prepared tomato sauce into the bottom of a 9x13 inch baking dish. Arrange the stuffed poblano peppers in a single layer over the sauce. Pour the remaining sauce over the peppers.
Step 8: Bake for 20-25 minutes, or until the peppers are tender and the cheese is melted and bubbly. If desired, sprinkle with cotija cheese during the last 5 minutes of baking.
Step 9: Remove from oven, garnish with fresh cilantro, and serve hot with your favorite Mexican sides.