In a small bowl, combine rolled oats, almond flour, coconut flour, and turbinado sugar. Add vegan butter and rub it into the dry mixture between your fingers. Keep in fridge until needed.
Make the muffins
Preheat the oven to 375°F. Lightly grease a 12-cup muffin tin or use paper liners.
In a small bowl, make the flax egg by combining flaxseed meal and warm water.
In a large mixing bowl, sift the whole wheat pastry flour, baking powder, cinnamon, cardamom, and sea salt.
In a medium mixing bowl, add coconut sugar, coconut milk, applesauce, vanilla extract, and lemon zest. Combine with a whisk, and mix in the flax egg.
Add the wet ingredients to the dry ingredients. Stir in strawberries and rhubarb until just combined.
Divide the muffin batter evenly between the 12 muffin cups. Sprinkle each muffin with one teaspoon of the crumb topping mixture.
Bake for 22-25 minutes or until a toothpick inserted comes out with moist crumbs attached.
Cool in muffin tins for 20 minutes and then remove muffins to a cooling rack.
Notes
Muffins will keep covered on counter for up to 3 days. Freeze for up to 1 month.The calorie count includes the crumb topping.