Fill a large pot with water, stir in 1/2 teaspoon salt, and bring to a boil. Stir in penne and return to a boil. Cook pasta uncovered, stirring occasionally, until cooked through but still firm to the bite, about 11 minutes; drain, reserving 1/2 cup of pasta-cooking water.
Clean and rinse zucchini blossoms, removing the inner parts (stigma or anthers); coarsely chop the flowers.
Heat olive oil in a large skillet over medium-low heat; cook and stir garlic in the hot oil until it begins to brown, 3 to 5 minutes. Stir parsley, saffron, and reserved 1/2 cup of pasta-cooking water into skillet; stir to combine. Add zucchini blossoms and simmer until tender, about 10 minutes. Sprinkle cornmeal into mixture and stir constantly until thickened, about 5 minutes.
Gently fold penne pasta into zucchini blossom mixture and top with Parmesan cheese, salt, and black pepper.