Bring a large pot of well-salted water to a boil.
Meanwhile, heat the olive oil in a 10- to 11-inch straight-sided sauté pan over medium heat. Add the fennel and garlic and cook, stirring occasionally, until the fennel starts to soften and brown, about 5 minutes. Stir in 1 cup water and the cream, chicken broth, sun-dried tomatoes, pepper flakes, and 1 tsp. salt. Bring to a boil, reduce the heat, and simmer briskly, uncovered, until the tomatoes are plump and soft, about 15 minutes.
Remove from the heat and stir in the Pernod, if using. Let cool slightly and then purée in a blender until smooth. Wipe out the skillet, return the sauce to the skillet, season to taste with salt, and keep hot.
Cook the rigatoni until just barely al dente, 1 to 2 minutes less than package instructions. Drain well and return to the pot. Add the sauce and toss over medium-low heat for a minute or two so the pasta finishes cooking and absorbs some of the sauce.