Unusual Pasta Sauces

See notes at the bottom regarding pasta that is appropriate for diabetics and keto dieters.

Pumpkin Spaghetti Sauce

Ingredients -- Ovo-Lacto Vegetarian

1 large can unsweetened Pumpkin Puree (unsweetened pumpkin pie filling) – typically 16 oz.
An Equal Amount (1 large can) Spaghetti Sauce or tomato sauce (16 oz.)
1/2 cup (1 stick) unsalted butter, at room temperature (can substitute olive oil or coconut oil)
3 or more large garlic cloves, finely chopped
(optional) finely diced vegetables e.g. onions, mushrooms, carrots, etc.
1/4 tsp. crushed red pepper (e.g. packet of leftover red pepper flakes from takeout pizza); and/or paprika or ground red pepper to taste, if you like spice
1 tsp. cinnamon
1/4 tsp. fresh grated nutmeg
Freshly ground black pepper to taste – at least 1/4 tsp.
1/2 cup fresh basil leaves, coarsely chopped
1/2 cup fresh Parmesan cheese
1/2 tsp. salt, or to taste

The original recipe called only for combining these ingredients over boiling water (i.e., in the top pan of a double boiler) without the tomato sauce.
I prefer sautée-ing the various vegetables and spices in the butter and/or oil in a very large saucepan, then adding the other ingredients in the order above. Stir well, heat to a bubbling boil and simmer for fifteen minutes to half an hour. Stir frequently while simmering so the cheese doesn’t burn on the bottom of the saucepan.
Very filling and tasty.

Sesame Spaghetti Sauce

Ingredients -- Vegan

2 Tbsp Chinese soy sauce
2 Tbsp Chinese oyster sauce (note: this is vegan, it's made from oyster mushrooms, not real oysters)
1 Tbsp Japanese sesame oil
1 Tbsp canola / vegetable oil
1+1/2 Tbsp keto sugar substitute, e.g. coconut sugar, allulose with monkfruit, etc.
1 tsp. Garlic paste with chili
Chives
1 jar (or 7 ounces) roasted red peppers, drained and cut lengthwise into 1/4-inch wide strips

Combine soy sauce, oyster sauce, sesame oil, canola oil, sugar, and chili paste in a serving bowl. Set aside to warm to room temperature. Cook pasta al-dente and drain well. Immediately add to the sauces in the bowl. Sprinkle with chives and the red pepper strips; toss until most of the liquid is absorbed.

Notes on Pasta for Keto dieters and diabetics

Regular pasta made from semolina wheat is not good for diabetics. But some work-arounds are available.
Some types of low-carb pasta, such as Banza or Ancient Harvest, are made with ingredients such as chickpeas and quinoa. These are _better_ for diabetics but still contain carbs. Shiritake pasta a.k.a. "miracle noodle" made from a mushroom, is sold packaged in water, has zero carbs, is terribly expensive, has a somewhat different taste & texture than real pasta. But it is healthy and works well in recipes. "Carbe Diem" brand spiked my blood sugar severely, (an example of how labeling of Keto and low-carb products doesn't always guarantee results, and people's metabolism differs). Palmini imitation pasta is made from hearts of palm and is healthy, but too stiff and fibrous unless cooked thoroughly (might work well for lasagna sheets).
If you prefer something more natural, cooked spaghetti squash works well for most tastes. It can also be part of breakfast or dessert recipes, such as savory breakfast fritters with eggs (add to the Japanese cabbage pancakes I mentioned). I have a recipe for spaghetti squash coconut pie.
Some types of Asian noodles, e.g. made with Sweet Potato or Mung Bean instead of semolina flour, can be lesser-carb substitutes for real spaghetti. But Asian noodles can vary _GREATLY_ in carb content, even the same type of noodle but different brands. Look at the nutrition labels and try to find Asian noodles with less than 30g carbohydrates per serving. Some can go as high as 90g.
See also my Dinner recipe for Keto lasagna.