Heat oven to 200°C. Toss the trimmed rhubarb pieces with 2 oz sugar and cinnamon on a baking tray, then cover with foil. Bake for 15 minutes, remove foil, stir gently, and bake uncovered for another 5 minutes until the rhubarb begins to break down. Pour the rhubarb into a fine-mesh strainer set over a bowl, reserving both the cooked rhubarb and the liquid separately—this separation is key to preventing a soggy cake while building a flavorful glaze. Set aside to cool slightly.

While the rhubarb cooks, lower the oven to 180°C and line a 9x13 inch baking dish (or similar cake tin) with parchment paper. Measure out all dry ingredients—flour and baking powder—and whisk them together in a small bowl. Have the room-temperature eggs, yogurt, vanilla extract, and softened margarine ready at your station. I like to use quality ingredients here: Imperial margarine has better water content for consistent results, and Greek yogurt creates a denser, more tender crumb than regular yogurt.

Beat the softened margarine with 8.8 oz sugar until light and fluffy, about 3-4 minutes—this aerates the batter and creates a tender cake. Add room-temperature eggs one at a time, beating well after each addition to fully incorporate before adding the next. Once the eggs are combined, add the vanilla extract and yogurt, mixing until just combined. Finally, gently fold in the dry ingredient mixture from Step 2 until no flour streaks remain—overmixing at this stage toughens the cake, so use a light hand.

Pour half of the batter from Step 3 into the prepared baking dish, spreading it evenly. Distribute the cooled rhubarb compote from Step 1 evenly over the batter, then carefully spread the remaining half of the batter on top, creating a protective layer that seals in the fruit. Bake at 180°C for 40 minutes uncovered, then cover with foil to prevent over-browning and bake for another 15-20 minutes until a toothpick inserted into the cake (avoiding the fruit) comes out clean. The foil prevents the top from darkening too much while the interior finishes cooking.

Remove the cake from the oven and let it cool in the pan for 10-15 minutes before turning out onto a wire cooling rack to cool completely. Meanwhile, pour the reserved rhubarb liquid from Step 1 into a small saucepan and bring to a boil over medium-high heat. Simmer for 5-10 minutes, stirring occasionally, until it reduces and thickens into a glossy glaze—it should coat the back of a spoon. Let the glaze cool for a few minutes before drizzling over the cooled cake.