For the crumble: Mix the flour, sugar and salt in a bowl.
Add the butter in pieces and knead with your fingers until crumbles form.
Place in the fridge until ready to use.
Wash the rhubarb, peel if necessary and cut into small pieces.
For the muffin batter: Combine the flour, sugar, salt, baking powder and baking soda in a mixing bowl.
In another bowl, mix eggs, oil, yoghurt, lemon juice, and vanilla (use a whisk for best results). Just until ingredients are fluid and well mixed.
Add the fluid mixture to the flour mixture and stir well.
Finally stir in the rhubarb.
Line a muffin tin with paper liners.
Divide the muffin batter into 12 muffins.
Scatter the sprinkles on top.
Bake in a preheated oven at 180°C for about 30-35 minutes. Do a toothpick test.
Let the muffins cool on a wire rack.