NYTimes Spicy pizza sauce

Makes about 1 quart. Half-recipe amounts (1 pint) are in parentheses.

The recipe is from the New York Times Cooking site.

INGREDIENTS
5 Tbl unsalted butter (2-1/2 Tbl)
(depending on how spicy-hot you want it) 1-2 Tbl red chile powder or flakes (any mix of gochugaru, togarashi, Aleppo pepper, Espelette pepper and red-pepper flakes, plus 1 tsp smoked paprika)(1/2 or 1 Tbl)
28-oz can whole plum tomatoes, crushed with your hands. Keep the unrinsed can (14-15 oz can)
1 large red or yellow onion, quartered lengthwise and peeled (1/2 red or yellow onion)
a 2-inch square Parmesan rind (1-inch)
1 tsp salt (1/2 tsp)
1 tsp granulated sugar (optional; 1/2 tsp)
water


PREPARATION

1. In a large saucepan over medium heat, melt the butter, then add the chile powder and stir until fragrant, just a few seconds (be careful not to burn the chiles).

2. Add the prepared tomatoes, along with 1/2 cup water swished around the can to catch any clinging sauce.

3. Stir in the onion, Parmesan rind, 1 tsp salt, and the sugar if using.

4. Bring to a boil, then lower the heat to simmer.

5. Partially cover and cook, stirring occasionally, until the sauce is thick and jammy, about 45 minutes.

6. Discard or eat the onion; discard the rind.

7. Taste and add more salt or sugar as needed.

8. Use right away or store in a tightly sealed container. The sauce should keep for up to 5 days in the refrigerator (and is even easier to cook with when cold).