Preheat oven to 350 degrees. Line a muffin pan with silicone baking cups or paper liners. Set prepared pan aside.
In a mixing bowl, whisk together the flour, sweetener, baking powder, cinnamon, salt, nutmeg and cloves. Set aside.
In a separate bowl, whisk together the wet ingredients; pumpkin, eggs, yogurt and vanilla. Gradually add the dry ingredient mixture to the wet ingredients using a whisk. Once all dry ingredients are well incorporated, batter will be very thick.
Spoon the batter into the prepared muffin pan, filling each cup a little over 3/4 full.
Mix together the crumble topping; in a bowl, combine the 1/2 cup flour, Swerve, cinnamon and salt. Add in the melted butter and mix together with a fork. The mixture will be crumbly and gravel-like. Sprinkle the mixture over the muffin batter.
Bake the muffins at 350 degrees for 18-20 minutes or until a toothpick inserted into the center of a muffin comes out clean and crumb-free.
Let muffins cool at room temperature 15 minutes before serving.