Fill a stockpot with water and the salt, and bring it to a boil. Add pasta, and cook until just al dente.
Reserve 1 cup of the pasta water, and drain the pasta. Set it aside in the colander. Pour about 1/2 cup of the reserved pasta water into the pesto, and stir to combine.
Return the pot to the stove, and heat the oil over medium high heat. Add the shrimp to the pan in a single layer, and flip them over in about 20 seconds. As soon as they are pink, add the cream to the pan and reduce the heat to medium.
Add about 2 tablespoons of the pesto to the shrimp and cream, and stir it in. Then stir the remainder of the pesto into the shrimp.
Add the cooked pasta to the shrimp and pesto cream sauce and stir to combine. If necessary, add additional pasta water to thin the sauce.
Mix the diced tomatoes into the pasta.