Not-Your-Mama's Tuna Salad

Ingredients
- 1 tub store-bought pesto sauce (1 cup), such as Contadina brand
- Juice of 1 lemon
- 2 cans tuna in water (6 ounces each)
- 4 scallions, cut with kitchen scissors or chopped
- 1 whole roasted red pepper, cut up with kitchen scissors or chopped
- A handful of grape tomatoes, halved with small paring knife
- 1 pound medium shell pasta, cooked to al dente and cooled by running under
- Cold water
- Salt and pepper