Ingredients
2 tablespoons extra-virgin olive oil
3 cups finely chopped onion (from 1 large)
Kosher salt
2 tablespoons minced garlic (4 to 5 cloves)
1/2 teaspoon red-pepper flakes
2 cans (each 28 ounces) whole peeled tomatoes in juice, pureed in a blender or food processor
1 1/2 pounds shrimp, peeled and deveined
3/4 cup panko flakes
1/4 cup whole milk
1/3 cup finely grated Pecorino Romano (1 ounce), plus more for serving
1/4 cup chopped fresh basil leaves, plus more for serving
1/4 cup chopped scallions, plus more green tops for serving (from 1 bunch)
1 large egg, lightly beaten
Kosher salt and freshly ground pepper
1 pound spaghetti, spaghettini, or bucatini
Preparation
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.
