Bring a large pot of lightly salted water to a boil. Cook angel hair pasta in the boiling water, stirring occasionally, until tender yet firm to the bite, 4 to 5 minutes. Drain.

Melt butter in a skillet over medium-high heat. Saute mushrooms, onion, scallions, and garlic until onions are translucent, about 5 minutes. Add wine, broth, tomatoes, and parsley. Bring sauce to a boil. Stir and reduce heat to low. Simmer, covered, for 10 minutes.

Place shrimp and flour in a resealable plastic bag; shake and mix until shrimp is well coated. Stir shrimp into the scampi. Cook until shrimp are opaque, about 5 minutes. Pour sauce and shrimp over the pasta; squeeze lemon juice on top. Season with salt and pepper.