Preheat your oven to 350°F (175°C). Prepare muffin tin by lining with paper liners or greasing.

In a mixing bowl, combine almond flour, coconut flour, baking soda, salt, and cinnamon. Whisk until well incorporated.

In another bowl, whisk together eggs, Greek yogurt, melted coconut oil, monk fruit sweetener, and vanilla until smooth.

Pour the wet mixture into the dry ingredients and stir until just combined; do not over-mix.

Fold in the chopped rhubarb until evenly distributed.

Divide the batter evenly into muffin cups, filling each about ¾ full.

Bake for 20–25 minutes or until golden brown. A toothpick inserted should come out clean.

Cool for 5–10 minutes before transferring to a wire rack to cool completely.