Heat the oil over medium-high heat in a large sauté pan until shimmering. Season shrimp and scallops with salt and add to pan. Sauté for 2-3 minutes each side until shrimp turns pink and scallops are well caramelized. Remove from pan and place in a covered dish.
Add the garlic, anchovy, and pepper flakes stirring constantly until fragrant, about 1 minute. Add tomatoes and chicken stock. Bring to a boil.
Reduce the heat to medium-low and add spaghetti. Simmer uncovered, stirring occasionally, until the pasta is al dente and the sauce thickens and clings to it, about 9-10 minutes. Add the shrimp, scallops, olives, and capers, and toss to combine. Heat through for 1-2 minutes. Serve.
Notes
Wash and drain the shrimp and scallops thoroughly. Dry with paper towels. The dryer the surface, the more caramelization (and flavor) builds.For an extra rich sauce, deglaze the pan with a 1/4 cup of white wine after adding the garlic, anchovy, and red pepper flakes.Green olives or black olives? Doesn't matter! Use your favorite--or a bit of both!