Preparation Combine anchovies, garlic, oil, and red pepper flakes in a large skillet. Cook over medium heat, stirring often, until anchovies have disintegrated into oil and garlic is lightly browned, 6–8 minutes. Meanwhile, cook pasta in a large pot of boiling salted water, stirring occasionally, until al dente. Drain, reserving 1 cup pasta cooking liquid. Remove skillet with anchovy mixture from heat and stir in butter and lemon juice until butter is melted. Add pasta and 1/2 cup pasta cooking liquid and stir constantly until a thick glossy sauce forms, adding more pasta cooking liquid as needed. Place radicchio in a large bowl. Add pasta and sauce and toss to coat, adding more pasta cooking liquid as needed. Add arugula and basil but don’t toss; season with salt and black pepper. Divide pasta among plates or bowls, very gently tossing so arugula gets coated in sauce but doesn’t wilt too much.
Preparation Combine anchovies, garlic, oil, and red pepper flakes in a large skillet. Cook over medium heat, stirring often, until anchovies have disintegrated into oil and garlic is lightly browned, 6–8 minutes. Meanwhile, cook pasta in a large pot of boiling salted water, stirring occasionally, until al dente. Drain, reserving 1 cup pasta cooking liquid. Remove skillet with anchovy mixture from heat and stir in butter and lemon juice until butter is melted. Add pasta and 1/2 cup pasta cooking liquid and stir constantly until a thick glossy sauce forms, adding more pasta cooking liquid as needed. Place radicchio in a large bowl. Add pasta and sauce and toss to coat, adding more pasta cooking liquid as needed. Add arugula and basil but don’t toss; season with salt and black pepper. Divide pasta among plates or bowls, very gently tossing so arugula gets coated in sauce but doesn’t wilt too much.