Cook the tortellini according to package instructions, then drain or keep warm in a little cooking water if desired.
Heat the olive oil and butter in a large stainless steel pan over medium heat.
Add the diced onion and cook until soft and translucent, about 3–4 minutes.
Add the minced garlic and cook about 1 minute until fragrant.
Stir in the crushed tomatoes (including juices), salt, pepper, garlic powder, onion powder, red pepper flakes, thyme, oregano, cumin, dried basil, and sugar; simmer for about 5 minutes.
Add the fresh spinach all at once, cover, and allow it to wilt, stirring occasionally; add water 1/4 cup at a time if the sauce becomes too dry.
In a small bowl, whisk together the flour, milk, and heavy cream until smooth, then pour the mixture into the tomato and spinach sauce and stir to combine.
Add the grated Parmesan to the sauce and stir until incorporated and heated through.
Use a slotted spoon to transfer the cooked tortellini into the sauce, gently stirring to coat without tearing the pasta; heat until everything is hot throughout.
Serve immediately and garnish with extra Parmesan and fresh basil if desired.