Bring a large pot of lightly salted water to a boil. Add fettuccine and cook for 8 to 10 minutes or until al dente; drain.
Meanwhile, heat 2 tablespoons of oil in a large skillet over medium-high heat, add the onions, squash, zucchini, and mushrooms; cook and stir for 5 minutes, until the vegetables are heated through but still firm. Pour in the cream and the cooked fettucine and simmer for 4 minutes. Mix in the jalapeno, garlic, mustard, and Cajun seasoning and cook for 1 minute. Stir in the Parmesan cheese and the tomatoes. Reduce the heat to low.
Preheat 3 tablespoons of oil in a large skillet over high heat. Dredge the rattlesnake meat in flour and pan fry for 5 minutes or until well done. Arrange the meat on top of the vegetables and pasta to serve.