Preheat the oven to 400°F. Lightly coat a 12-cup muffin pan with nonstick cooking spray, or place a paper liner in each cavity.
Add the Bisquick baking mix, pumpkin pie spice, and Truvia Baking Blend—or granulated sugar—to a mixing bowl. Whisk until the dry ingredients are evenly distributed and no noticeable clumps remain.
In a separate bowl, combine the milk, pumpkin purée, egg, and canola oil. Whisk thoroughly until the mixture appears smooth and consistent.
Pour the pumpkin mixture into the bowl containing the dry ingredients. Stir or whisk only until the ingredients are incorporated. The finished batter should retain a slightly lumpy texture.
Divide the batter among the prepared muffin cups, filling each cavity approximately two-thirds full.
Bake for 15–20 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Allow the muffins to rest in the pan for several minutes. Transfer them to a wire cooling rack and serve either warm or at room temperature.