Cook pasta until al dente according to package directions. Drain and reserve 2 cups of pasta water. Place pasta back in the pot and stir in 1/4 cup of reserved pasta water.
While the pasta is cooking, use a large skillet on medium high heat and add the pancetta or bacon. Cook until the fat starts to render, 6 to 8 minutes. Add the minced garlic, stirring for 1 minute until fragrant.
Add the cauliflower florets to the skillet and stir to coat with the rendered fat. Add the red pepper flakes. Stir occasionally to soften and lightly brown the florets, 6 to 8 minutes.
Add 1/4 cup of the reserved pasta water to the skillet, lower the heat to low, and add the grated Parmesan cheese. Stir until the cheese is melted, gradually adding more water as necessary until you have a creamy sauce that coats your stirring utensil.
Add the pasta to the skillet and stir to combine. Taste and add salt, up to 1/2 teaspoon as desired. Serve hot.