Cook the pasta according to package directions. Drain well and rinse with cold water. Let cool.

Add the pasta, tomatoes, spinach, mozzarella, and shallot to a serving bowl.

Make the dressing: add the sun-dried tomatoes (with their oil) to a food processor or blender. Add the garlic, 1 teaspoon red pepper flakes and 1/2 teaspoon salt. Pulse until sun-dried tomatoes are finely chopped, then run the food processor or blender while adding the olive oil. Run until a thick sauce forms. Taste, then add more pepper flakes and/or salt to taste.

Toss pasta with sauce.

Store in refrigerator for up to 3 days.