Preheat your oven to 180ºC (fan) or 200ºC (non-fan). Line your muffin tin with paper liners.

Wash and slice rhubarb into 3cm pieces, toss with sugar and roast for 20 minutes, uncover for another 5 minutes. Drain excess moisture.

Sift together flour, baking powder, and sugar in a large mixing bowl. Whisk until well combined.

In a separate jug, whisk yogurt, vegetable oil, and egg until smooth, then combine with dry ingredients carefully.

For the crumble topping, rub margarine into flour and sugar until it resembles coarse breadcrumbs.

Spoon muffin batter into lined tins, add roasted rhubarb on top, and sprinkle crumble mixture.

Bake the muffins for approximately 20 minutes, or until golden brown and a toothpick comes out clean.

Allow muffins to cool in the tin for 10 minutes, then transfer to a wire rack to cool completely.