- In a medium bowl whisk together the lemon juice, garlic and olive oil. Add the shrimp and toss well. Set aside while you prepare the other ingredients. 
- Boil the pasta in a large pot of boiling salted water. I use 2 tablespoons of salt in the pot. 
- Cook the pasta for the length of time on the package minus one minute. We want it to be quite al dente. 
- Rinse the cooked pasta under cold water, drain and set aside. 
- Cook the shrimp on a grill or in a hot frying pan until charred, about 2 minutes on each side. 
- In a large bowl mix together the pesto and ricotta. Add the pasta and mix well. 
- Add the onion, tomatoes and shrimp and mix gently. 
- Top with the crumbled feta (if using) and serve.