Preheat the oven to 450 degrees F. Place the potatoes on a large rimmed baking sheet and drizzle with 1 tablespoon olive oil. Shake the pan to coat the potatoes in oil, the salt and pepper liberally. Roast in the oven for 30 minutes, until the skins are crispy, but the flesh in tender.
Meanwhile, add the remaining olive oil to a skillet. Heat to medium, and add the onions and poblano peppers. Saute for 3-4 minutes, stirring occasionally. Then add the garlic and salt and pepper to taste. Saute another 3-4 minutes, until the peppers are soft.
Once the potatoes are tender, remove them from the oven and use a flat metal spatula to press them flat, about 1/3- to 1/2-inch thick. Spread them out on the baking sheet and spoon the pepper mixture over the top of each smashed potato. Then sprinkle with crumbled queso fresco.
Place the pan back in the oven for 5-10 minutes, until the cheese starts to toast. Serve warm.