Put peppers and vinegar in a small bowl. Let stand.
Heat oil in a large skillet over medium heat. Season pork with salt and pepper and add to hot oil. Cook, turning once, until browned, about 8 minutes.
Add onion to skillet. Cook, stirring often, until just softened, about 2 minutes. Reduce heat to low and add A.1.® Original Sauce, brown sugar, and 1/4 cup water. Cook, stirring, until bubbling. Cover and cook, turning pork once, for 10 minutes.
Stir in tomatoes, cover, and cook until some tomatoes begin to burst, about 5 minutes. Divide among serving plates. Drain peppers and scatter on top. Serve immediately.