Although cooking pasta in the microwave is a relatively simple process, it's easy to wind up with mushy, overcooked pasta if you aren't paying attention. The type of pasta you are cooking is a factor, as short, sturdy pasta noodles such as penne rigatone do not cook at the same rate as long, delicate noodles like spaghetti or angel hair pasta. Paying attention to the pasta-to-water ratio and periodically checking the firmness of the noodles is crucial to properly cooking penne rigate and similar pasta types in the microwave.
Fill a 3-quart microwave-safe baking dish with water and microwave on high until it reaches a full boil. For 1/2 pound (8 ounces) of uncooked pasta, use 5 to 6 cups of water.
Add the penne rigate pasta noodles to the hot water along with 1/2 teaspoon of salt.
Return the dish to the microwave and cook on high for 10 to 15 minutes, until the pasta is al dente, meaning it is still slightly firm to the touch. Depending on the wattage of your microwave, it may take a little less or a little more time for the pasta to cook, so stop the microwave to check the firmness of the noodles every few minutes.
Remove the noodles from the microwave when they're ready and drain in a colander. Return to the casserole dish and toss with your favorite pasta sauce, or serve the sauce on the side. One-half pound of uncooked penne rigate makes roughly 4 cups cooked.