Preheat oven to broil with oven rack about 6 inches from heat. Place bell peppers and tomato on a large rimmed baking sheet. Broil, turning twice, until charred on all sides, 10 to 15 minutes. This can also be done on a grill which is what I did.
Transfer charred peppers to a bowl, and cover with plastic wrap; let stand 30 minutes.
Remove skin from tomato; quarter tomato. Remove skin, seeds, and stem from bell peppers. Process bell peppers, tomato, pecans, cilantro, garlic, lemon juice, vinegar, smoked paprika, and cayenne in a blender until smooth, about 2 minutes. With blender running on low speed, gradually add oil; process until smooth, about 30 seconds. Stir in salt.