Preheat oven to 375°F convection or 400°F without convection. Butter and flour a muffin tin or line with baking cups/muffin papers.

Using a fork, gently mix all ingredients for crumble topping in small bowl and set aside. (Do not break up pieces. Leave big chunks, it will make a better topping.)

Whisk flour, baking powder, baking soda, and salt in a medium bowl and set aside.

In a separate bowl, whisk eggs with sugar, then add butter, vanilla, yogurt, blood orange zest and blood orange juice. Whisk to combine.

Pour wet ingredients into dry and stir with rubber spatula until almost fully combined.

Using a 2 ounce measure (1/4 cup) portion batter evenly into muffin cups. (Muffin cups should be about 2/3 full).

Sprinkle crumble topping evenly over muffin batter.

Bake for 18 - 20 minutes, or until a tester comes out with a few crumbs attached.

Cool completely on cooling rack.

When muffins have cooled, stir powdered sugar and blood orange juice together to make the glaze and drizzle over the muffins.