Mix together the mayonnaise, sour cream, grated parmesan, sugar, and onion powder. Set aside.
Salad
In a clear glass trifle bowl cover the bottom with most of the chopped romaine, reserving a little to fill in the center of the bowl.
Layer diced tomatoes, sliced green onions, chopped hard-boiled eggs, and peas on top of the lettuce. Concentrate ingredients on the other edges of the bowl and use reserved chopped romaine to fill in the center to keep the layers even.
Spread the prepared dressing over the peas layer.
Top with the shredded cheddar cheese and crumbled bacon.
Cover and refrigerate for several hours or overnight. Toss before serving, if desired.