Wash and dry all produce. Bring a large pot of salted water to a boil. Halve, peel, and dice onion. Pick leaves from oregano. Discard stems and finely chop leaves. Mince or grate garlic.

Heat a drizzle of olive oil in a large pan over medium-high heat. Add garlic, onion, half the oregano, and a pinch of chili flakes (to taste). Cook until softened, about 5 minutes, tossing occasionally. Season with salt and pepper.

Add diced tomatoes and 1/2 tsp sugar to pan. Reduce heat to medium-low and let simmer until thickened, about 10 minutes. Season with salt and pepper.

Once water is boiling, add linguine to pot. Cook until al dente, 9-11 minutes. Drain, reserving 1/4 cup cooking water.

Season shrimp with salt and pepper. Add to pan and stir into tomato sauce. Let shrimp cook until pink and completely opaque, 4-5 minutes.

Toss linguine into pan, coating with sauce. Add a splash of cooking water if necessary to give tomatoes a saucy consistency. Season with salt and pepper. Divide linguine and shrimp between plates. Sprinkle with remaining oregano and any additional chili flakes, if desired.