In a large skillet with a lid, heat oil over medium-high. Season lamb generously on both sides with salt and pepper. Place in skillet; cook until browned, 3 to 4 minutes per side (lamb will finish cooking in step 4). Transfer chops to a plate (keep oil in skillet); loosely cover with aluminum foil, and set aside.
To skillet, add onion, garlic, rosemary, and red-pepper flakes; season with salt and pepper. Cook, stirring frequently, until onion has softened, 3 to 5 minutes.
Add beans, sun-dried tomatoes, and 1/2 cup water. Bring to a boil, then reduce heat to medium-low; cook until mixture is slightly thickened and saucy, 4 to 6 minutes.
Place chops on top of beans in skillet (adding any juices that have accumulated on plate). Cover skillet, and simmer until meat is medium-rare, 3 to 4 minutes. Serve chops with beans, and garnish with rosemary, if desired.