In a large pot of salted water on medium high heat, bring water to boil. Add pasta and cook until al dente, about 6-8 minutes. Drain; reserving ½ cup of pasta water. Return pasta to pot and set aside.
In medium bowl, add broccoli florets and 3 tablespoons water. Cover with plastic wrap and microwave on high for 1 1/2 minutes. Drain and set aside.
In a large sauté pan on medium high heat, add olive oil, garlic and red pepper flakes. Cook for 1 minute. Add shrimp and cook for 3-5 minutes. Season with salt and pepper. Transfer shrimp to pot with pasta.
Add tomatoes to sauté pan and cook for 2-3 minutes. Season with salt and pepper. Add reserved pasta water and chicken stock. Bring to boil. Reduce heat to medium low and simmer until reduced by half, about 5-7 minutes. Add butter, half and half and lemon juice; stir to combine. Simmer for 1-2 minutes or until slightly thickened.
Add broccoli, pasta and shrimp to sauté pan. Toss to combine with sauce and reheat for 2-3 minutes.
Place in serving bowl and garnish with lemon zest, if desired.