1. Fill large pot with water. Quarter half the lemons and add to the water. Then add onion, garlic and seafood seasoning to water. Bring water to boil.
2. Clean and cut potatoes in half. Add the potatoes to the boiling water, cook for 10-12 minutes or until just barely fork tender.
3. Clean and cut corn, add to boiling water along with the sliced smoked sausage. Cook for 5-6 minutes.
4. Add shrimp to boiling water and cook an additional 2-3 minutes or until pink.
5. Drain water and place the shrimp mixture on a large baking sheet.
6. In a microwave safe bowl melt the butter. Add salt, pepper and chopped parsley to butter and whisk to combine.
7. Pour ½ of butter mixture over shrimp mixture and stir to coat. Reserve remaining butter mixture for serving.
8. Garnish with additional chopped parsley and lemons
9. Sprinkle additional seafood seasoning to taste, if desired
10. Serve immediately with reserved butter mixture.