In a 12-inch nonstick skillet over medium, heat 2 tablespoons of the oil until shimmering. Add the poblanos, scallions, garlic, Aleppo pepper, and ½ teaspoon each salt and white pepper. Cover and cook, stirring, until the chilies are softened but not browned, 6 to 8 minutes. Transfer to a medium bowl and stir in the tomatoes and capers; set aside. Wipe out the skillet.