Melt butter over medium/low heat in a large pan or Dutch oven.

Add onions and cook two minutes. Add garlic, stir, and cook for one minute. Whisk in the flour until all of it is absorbed into the butter. Cook roux for one minute.

Pour in the entire bottle of wine while whisking. Whisk until all the roux has broken down into the wine.

Add tomatoes, salt, pepper, Italian seasoning, and crushed red pepper. Mix well and bring to a simmer over medium/high heat. Simmer for an hour, stirring every so often.

During the last twenty minutes of the sauce’s cook time, bring a large pot of salted water to a boil. Drop the spaghetti and boil for seven minutes, then drain.

When the sauce is done cooking down, using an immersion blender, blend until all tomatoes and onions are pureed and the sauce is smooth.

Add the pasta to the sauce, mix, and then serve.