Preheat oven to 400 degrees F.
In a skillet, saute the onion in 1 teaspoon of oil and 1 teaspoon of butter until they are caramelized.
In a medium sized bowl, combine the panko crumbs with 3 teaspoons of chopped parsley and 1 teaspoon of melted butter, 2 teaspoons of olive oil, and the juice of half the lemon.
Once the onions are ready, add salt and pepper.
Add the lemon juice and the white wine to the onions and continue to cook for 1 minute.
Spread the onion and lemon mixture into a large casserole.
Place the fish on top of the onions, drizzle on a teaspoon of the olive oil and season the fish with salt and pepper.
Divide the crumb topping evenly over the fish and sprinkle with the rest of the parsley and toss on the cherry tomatoes.
Bake for about 20 minutes until fish is cooked through and the crumbs are nicely browned.