Heat your grill on high for at least 10 minutes.
Drizzle zucchini slabs with olive oil and sprinkle evenly with ½ teaspoon salt, then use your hands to rub all over. Place on the grill and cook, covered, for about 4 minutes or until you have nice grill marks. Flip and repeat for about 3 more minutes or until cooked through.
Transfer to a cutting board to cool off, then slice into bite-sized pieces. Transfer to a large bowl. As the zucchini sits in the bowl, it will give off a liquid - I like to drain/spoon this out so it doesn’t water down the sauce, but that is optional!
Bring a large pot of water to a boil and cook the tortellini according to the package instructions. Drain and transfer to the large bowl to let cool for a few minutes.
In a high-speed blender, add the tomatoes, vinegar, mustard, oregano, pepper, garlic, and remaining ½ teaspoon salt and blend until the tomatoes are all broken up. With the motor running, slowly pour in the olive oil and blend on high until smooth (be careful of splatter/wear an apron!).
Pour about ¾ of the dressing over the zucchini/tortellini and toss to coat. Serve topped with more dressing, parmesan, basil (if using), walnuts (if using), and black pepper.