In a medium microwave-safe mixing bowl, melt the butter. Add the yogurt, eggs, pumpkin pie spice extract, and espresso powder. Using a hand mixer, blend until smooth.
In another medium mixing bowl, toss together the almond flour, Swerve, baking powder, and pumpkin pie spice. Add 1/4 of this mixture to the wet ingredients and blend with the hand mixer until just barely smooth. Repeat with another 1/4, and continue repeating until the mixture is blended. Do not overblend--as soon as the dry ingredients are incorporated, stop mixing.
Grease 12 silicone muffin liners with butter or coconut oil. Fill each one 2/3 full with the batter. Place them on a cookie sheet and tap it on the counter a few times to settle the batter. Bake for 22-25 minutes. Remove from the oven and let cool on a baking rack.
Macros per serving (1 muffin): 220 calories, 3 net carbs, 6 grams protein, 20 grams fat.