Cook spaghetti according to package instructions in a large pot of lightly salted water. Once al dente, strain and lightly dress the pasta in olive oil to keep noodles from sticking together.
While the pasta cooks, start the sauce. In a medium saucepan, add tomatoes. Rough crush the tomatoes with your hands. Add butter and onion. Set to simmer on low heat for 30-45 minutes, stir occasionally. Before straining the pasta, add 1/4 cup of the pasta water to the tomato sauce. The starchy water will help thicken the sauce.
About 10 minutes before you are ready to eat, start the scallops. Rinse the scallops, then pat them dry with a paper towel.
Make the scallops: In a large skillet (oven safe), add olive oil and heat over medium-high heat. Add garlic and sauté for about 1 minute until it gets fragrant.
Add scallops to skillet in a single layer. Sear for 20-30 seconds (seriously, that's it), Remove skillet from heat.
Turn your oven broiler to high. Add breadcrumbs, parsley and parmesan to the scallop skillet, and stir to combine. Add the skillet to the top rack of the oven and broil for a little less than one minute. This will help toast the breadcrumbs and finish cooking the scallops.
Finally, finish the sauce. Remove the onion pieces out of the sauce and discard.
Dress noodles with tomato butter sauce, then top with a scoopful of the scallop mixture.
Sprinkle with Parmesan cheese and fresh herbs (optional). Serve warm.