No beef or pork here! Just succulent shrimp amped up with panko, Pecorino Romano, fresh basil, and scallions and formed into balls. They're paired with our classic five-ingredient red sauce.
Red Sauce: Heat a straight-sided skillet over medium. Swirl in oil; add onion and 1 teaspoon salt. Cook, stirring occasionally, until onion is soft and translucent, 7 to 9 minutes. Stir in garlic and red-pepper flakes; cook 30 seconds. Transfer one-third of onion mixture to a bowl and reserve for meatballs. Add tomatoes to skillet; bring to a boil. Reduce heat and simmer, stirring occasionally, until reduced and thickened slightly, about 20 minutes.
Shrimp Meatballs: While sauce simmers, pulse shrimp to a paste in a food processor. Transfer to bowl with reserved onion mixture. Stir panko and milk into shrimp mixture until milk is absorbed. Add cheese, basil, scallions, egg, 1 teaspoon salt, and 1/4 teaspoon pepper. Refrigerate 30 minutes.
Use an ice cream scoop, or roll heaping tablespoons between dampened palms, to form thirty 1 1/2-inch balls. Drop into a pot of boiling salted water; cook until they turn opaque and float to top, 3 to 4 minutes. With a slotted spoon, transfer shrimp meatballs to skillet with red sauce and simmer until just cooked through, about 5 minutes.
Meanwhile, cook pasta in same pot of boiling water until al dente, about 2 minutes less than per package instructions. Drain pasta and return to pot; toss with 1 1/2 cups sauce. Serve, topped with meatballs, more sauce, cheese, basil, and scallion tops.