I started by sauteing carrots and onion. Both caramelize when cooked, so no additional sugar is necessary. I used my favorite vegetable broth as the base; chicken broth will also work unless you prefer your recipe to be vegetarian or vegan. You can make your own broths from scratch if you have the time; otherwise, snag one off the shelf when you grab the pumpkin. Many prepared broths are sodium-heavy; for the sake of healthy cooking, choose one labeled low or no salt. And before you stir in your can of pumpkin puree, double-check that you are, indeed, adding 100% pumpkin, not pumpkin pie filling. Otherwise your soup might taste a lot less like pumpkin and a lot more like a pumpkin spice latte.
If you are so inspired, you can flavor your soup in the traditional way, with a Scotch bonnet pepper. Simply place the whole pepper in the broth while the vegetables simmer, then remove it before serving. I actually prefer to use ground chile powder instead of the pepper, because I can control the heat level better.