Heat the oven to 350°F (175°C). Place paper liners into the wells of a muffin pan so they are ready for the batter.

Place the softened unsalted butter and Truvia Brown Sugar Blend in a large mixing bowl. Beat at medium speed until the two ingredients are thoroughly incorporated.

Add the eggs individually, beating after each addition until incorporated before adding the next egg. At this point, the mixture may look somewhat thin and lumpy.

Pour in the vanilla extract and add the pumpkin purée. Continue mixing at medium speed until evenly combined.

Add the almond flour, baking powder, pumpkin pie spice, and salt. Beat for approximately 2 minutes, or until the mixture develops a thick, smooth consistency without visible lumps.

Place the butter in a microwave-safe, heat-resistant bowl and microwave for 20–30 seconds, or until completely melted.

Stir in the almond flour, Truvia Brown Sugar Blend, and pumpkin pie spice. Whisk until the ingredients combine into an evenly blended, paste-like mixture.

Divide the prepared pumpkin batter among the lined muffin cups, filling each liner to the top. Use approximately ⅓ cup of batter per muffin, as these muffins do not rise substantially during baking.

Spoon roughly 2 heaping teaspoons of crumble mixture over each portion of batter. Press the topping down gently so it adheres to the surface.

Bake in the preheated oven for 25–30 minutes. The muffins are finished when a knife inserted into the center comes out clean.

If the muffin tops begin browning before the centers are fully baked, loosely cover the pan with aluminum foil to limit additional browning.

Allow the muffins to cool completely to room temperature before handling or serving. Cooling gives the crumble topping time to firm and develop its intended texture.

After the muffins have cooled, the topping should have hardened. If desired for the intended crumbly finish, carefully lift the firm topping from the muffins, break it into crumbs with your fingers, and scatter the pieces back over the tops.