Make the shrimp

1. In a very large skillet, heat the olive oil. Add the garlic and cook over moderately high heat until light golden, about 2 minutes. Add the crushed red pepper and cook for 30 seconds. Add the shrimp and cook, stirring occasionally, until white throughout, about 4 minutes. Season with salt and pepper. Add the lemon juice and butter and cook over low heat until the butter is melted and the sauce coats the shrimp. Reserve half of the shrimp and sauce for the pasta, and store the remainder for later use.

Make the pasta

1. In a large pot of boiling salted water, cook the capellini until al dente. Drain, reserving 1 cup of the pasta cooking water. Return the capellini to the pot. Add the reserved shrimp with their juices, along with the tomatoes, the capers, and the reserved pasta cooking water. Toss over low heat until the shrimp are heated through and the pasta is well coated. Season with salt and pepper and serve.