Heat oil in a large saucepan over medium heat. Stir in onion; cook, stirring occasionally, until translucent, about 4 minutes. Stir in garlic, Italian seasoning and crushed red pepper; cook, stirring constantly, until fragrant, about 1 minute. Stir in tomato paste; cook, stirring constantly, until all the vegetables are coated, about 1 minute. Pour in wine; cook, stirring once or twice, until reduced by half, about 2 minutes. Stir in broth, tomatoes, Parmesan rind and salt; bring to a boil over medium-high heat. Add tortellini; cook, stirring often, until the tortellini are tender, 3 to 5 minutes (or according to package directions). Remove from heat and add spinach; stir until wilted, about 1 minute. Remove and discard the Parmesan rind.