In a medium saucepan, cover the lentils with 3 inches of water. Add the halved onion and bay leaf; bring to a boil over high heat. Salt the water and cook the lentils until just tender, 20 to 22 minutes. Drain; discard onion and bay leaf.
While lentils are cooking, bring a large pot of water to a boil. Heat a large skillet over medium. Add the EVOO, four turns of the pan. Add the anchovies and stir until completely melted into the oil. Add the chopped herbs, garlic and crushed red pepper; stir for 2 minutes. Add the chopped onion and celery; season with salt and pepper. Cover and cook until onions soften, about 5 minutes.
While the anchovy sauce is cooking, salt the water and cook the pasta until al dente. Drain, reserving 1 cup of the pasta cooking water.
Add the pasta cooking water to the anchovy sauce, then toss with the drained pasta, adding the lentils, kale and lemon juice; season. Divide among bowls.