Bring a large pot of salted boiling water to a boil.

Cook penne according to package directions, until al dente.

Drain, reserving 1/2 cup pasta water, and return to pot.

Meanwhile, make pesto: In a food processor fitted with a metal blade, blend basil, walnuts, Parmesan, and garlic.

Slowly add olive oil in a steady stream.

Season with salt.

Add pesto and 1/4 cup pasta water to pot, stirring until saucy and creamy.

(Add more pasta water until you reach your desired consistency.

) Add tomatoes and feta and stir until combined.

Divide pasta among six mason jars and top with additional feta.