Capers are the flower bud of a Mediterranean bush. Caperberries are the fruit that blooms after it flowers. Both are rich in antioxidants.
Cook pasta according to package directions, omitting salt and fat. Drain, reserving 1/2 cup of the cooking liquid.
Melt butter in a large skillet over medium-high heat. Add artichoke hearts; cook, without stirring, until browned, 4 to 5 minutes. Add onion; cook, stirring occasionally, until beginning to brown, about 2 minutes. Add caperberries and garlic; cook, stirring occasionally, for 1 minute. Transfer mixture to a plate.
Add tomatoes, oil, and reserved cooking liquid to skillet; bring to a boil. Cook, stirring occasionally, until slightly thickened, about 6 minutes. Add pasta to tomato mixture and cook, stirring to coat, for 1 minute. Stir in artichoke mixture and arugula. Sprinkle servings with cheese.