1. In a large pot of boiling salted water, cook the penne until al dente. Drain, reserving 1 cup of the cooking water.
2. Meanwhile, in a large skillet, heat the oil until shimmering. Add the red peppers, garlic and crushed red pepper and cook over moderately high heat until the peppers are softened, 6 minutes. Add the escarole and cook, stirring, until wilted, 3 minutes. Stir in the tuna.
3. Add the pasta, the reserved cooking water and 1/2 cup of the Parmesan to the skillet and cook, tossing, until the liquid is nearly absorbed, 2 minutes. Transfer to bowls, sprinkle with the remaining 1/4 cup of Parmesan and serve.