Pre heat the oven to 220C and line a muffin tin with 12 cupcake cases. Set to one side.
In a large bowl mix together the rhubarb and sugar. Place to the side whilst you make the crumble topping.
In a different large mixing bowl, stir together the dry topping ingredients (sugar, flour, cinnamon and oats). Then using your fingers rub the dairy free spread into the dry ingredients until you have a crumble mixture. Pop to the side whilst you make the muffin batter.
To the rhubarb/sugar mixture add the oil, vegan egg, yoghurt, and vanilla. Stir until fully combined. Then sift in the flour, baking powder, and bicarbonate of soda. Stir again until mixed through.
Evenly divide the batter between the 12 cupcake cases. Then sprinkle the crumble topping over the batter, pressing down gently to ‘stick’ it down.
Pop the muffins into the oven to bake for 15-20 minutes. To check the muffins are cooked through, insert a skewer into the centre- it should be clean when removed. Leave to cool slightly in the tin before transferring to a wire rack to cool fully.