Dice strawberries and rhubarb into small pieces. Set aside.
Mix together milk and lemon juice. Set aside.
In a medium size bowl, add flour, baking soda, baking powder and salt. Whisk to combine.
In a large bowl, add coconut sugar, Greek yogurt, eggs, vanilla and the milk mixture. Whisk to combine.
Add the dry ingredients to the wet ingredients. Using a spatula, fold dry ingredients into wet ingredients. Fold until the flour mixture is incorporated and there are no lumps in the batter.
Add diced strawberries and rhubarb. Use a spatula to fold in the strawberries and rhubarb.
Using a cookie scoop, divide batter evenly into prepared muffin pan. Optional: place thinly sliced strawberries on top of the batter.
Bake for 16-18 minutes or until a toothpick inserted into the center of a muffin comes out clean. Let muffins cool in the pan for 10 minutes before removing and transferring to a wire rack to cool completely. Makes 12 muffins.