Preheat oven to 450 degrees if using oven, or heat up grill.
For oven: Slice kernels of corn off the cob. Place on baking sheet. Toss with 1 tbls. olive oil and a little salt & pepper. Put shrimp on another baking sheet and toss with 1 tbls. olive oil and a little salt & pepper. Roast corn and shrimp until shrimp are pink and cooked through, about 6-8 minutes (stir halfway through cooking). For BBQ grill: drizzle olive oil, salt & pepper over corn and shrimp. Grill until cooked.
Put corn kernels and shrimp in large serving bowl.
Toss with pesto and let cool to room temperature.
Add diced tomatoes, stir to combine and serve.
If you don’t want to roast the corn and shrimp in the oven, you can grill them on a BBQ or grill pan, or cook them in a pot of boiling water.