In a large pot over medium-low heat, melt 2 tbsp olive oil and 2 tbsp butter. Add the finely chopped onion and sauté for 3–4 minutes, until softened but not browned.

Add the garlic and cook for 1 minute, stirring often.

Stir in the tomato paste and cook for 2–3 minutes, until it’s fully incorporated and deepens in colour, watching carefully so that it doesn’t burn.

Add the seasonings—red pepper flakes, oregano, salt—and stir for another minute to bloom the flavours.

Pour in the broth, increasing the heat to bring it to a gentle boil. Once bubbling, reduce the heat to low and add a parmesan rind and the pasta. This type of pasta takes about 15-20 minutes to cook on this lower heat. As the pasta cooks, it will release starch and naturally thicken the soup. If you prefer a brothier soup, add more broth to reach your desired consistency.

Once the pasta is tender, remove the parmesan rind and taste to adjust the seasonings. I like a squeeze of lemon juice to help balance the flavours, and you may want to add a bit more salt or pepper to finish.

Serve immediately with some grated parmesan, and you can also top with fresh basil and a crack of black pepper, if desired.