Preheat oven to 350 F. Prepare a standard 12 cup muffin tin with paper liners.
In a medium bowl, whisk yogurt, 2 Tbsp butter, oil, and egg.
In a large bowl, stir 3/4 cup brown sugar, almond flour, baking soda, and salt together. Pour the wet ingredients into the dry and fold until just combined. Fold in rhubarb, then divide batter into the prepared muffin tin, filling about 2/3 full.
In a small bowl, stir 1/4 cup brown sugar, nutmeg, cinnamon, 1 Tbsp butter, and almonds. Spoon mixture over the batter.
Bake 20-25 minutes, until a toothpick inserted in the center of the muffin comes out clean. Allow to cool in pan for about 10 minutes, then serve.