Add a tablespoon or so of olive oil to a hot pan over medium-high heat, throw in the red pepper flakes, garlic and onions and give them a stir. Add the wine (or chicken broth), whisking to deglaze the bottom of the pan. Cook until the liquid reduces by half. Add the crushed tomatoes and Italian seasoning and stir to combine. Add a pinch of sugar and some salt and pepper to taste. Reduce the heat to low and simmer for 30 minutes.
Let cool, then portion into 4 freezer bags and freeze.