Cook tortellini according to package directions; drain. Rinse with cold water; drain well in colander.
Meanwhile, for pesto, in a food processor bowl or blender container, combine the undrained tomatoes, half of the pepperoni, the water, mustard, garlic, lemon juice, and fennel seed. Cover and process or blend until smooth. If desired, season to taste with black pepper. Set aside. Halve the remaining pepperoni slices.
In a very large bowl, combine the cooked tortellini, tomatoes, yellow pepper, and halved pepperoni slices. Add the pesto mixture to the tortellini mixture. Toss gently to combine. Spoon onto a serving platter. Sprinkle with parsley and basil. Makes 12 side-dish servings.