Rinse and seed tomatoes while keeping as much of the canned juice as possible. Process tomatoes and thier juice in a food processor until pureed. The puree should not be completely smooth, but should have no chunks larger than 1/16”. Add sugar, vinegar, and cognac, and set aside.

Combine butter and oil in a medium sauce pan and heat over medium-low heat until butter is melted. Add garlic, dried spices, and salt, and cook, stirring frequently until fragrant but not browned, about 3 minutes.

Add tomato puree, basil sprigs, onion halves, and bring to a simmer. Reduce heat to lowest setting (bubbles should barely be breaking the surface), and cook, stirring occasionally, until reduced by half, about 1 hour. Season to taste with salt and more cognac if desired.

Allow to cool to room temperature and store in a covered container in refrigerator for up to 2 weeks, or freeze for up to 6 months.