Preheat the oven to 180 C / Gas 4. Lightly grease a 25cm pastry tin.
In a large bowl, beat butter and sugar together using an electric beater, until light and fluffy.
Add semolina and yogurt; stir to mix well and break up any lumps. Add baking powder and vanilla extract; mix well.
Spoon the cake mixture into prepared pastry tin, pressing it down and smoothing over the top. Use a heart shaped cookie cutter to create heart shapes within the cake so it is easier to remove them after cooking.
Bake in the preheated oven for 30 minutes.
Meanwhile, prepare the syrup. Place sugar, water and butter in a saucepan; simmer over medium-low heat for 10 minutes.
Remove the cake from the oven; carefully pour or spoon the hot syrup over the warm cake. Let the syrup absorb completely into the cake before removing the heart shaped smaller cakes.
Arrange heart cake on a plate and garnish with petals.