Melt 4 tablespoons of the butter in a 2-quart saucepan over high heat.
Add the onion, squash and zucchini and sauté until vegetables start to get tender, about 2 minutes, stirring occasionally.
Add cayenne & white pepper and continue cooking about 1 minute.
Add the lemon juice and fresh shrimp or crawfish and cook 1 minute.
Stir in the cream, the remaining 1 tablespoon butter and the Parmesan cheese.
Cook until heated through, stirring constantly.
Remove from heat and serve immediately, allowing about ½ cup sauce per serving. Serve over pasta or rice.
NOTE: *Julienned strips should be cut so that all squash and zucchini slices have skin on one surface.
NOTE : Very spicy, even when cayenne cut in half. Consider cutting in ¼.