1. Preheat your oven to 350°F (175°C).

2. Cut the rhubarb into small pieces and melt the butter in a saucepan over low heat.

3. Whisk the eggs and sugar together in a large bowl until the mixture is light and fluffy.

4. In a separate bowl, combine the flour, baking powder, and ground cardamom.

5. Add the flour mixture and melted butter to the egg mixture, alternating between the two and starting and ending with the flour mixture.

6. Pour the batter into a 9.5-inch (24 cm) springform pan that has been greased and floured.

7. Spread the rhubarb pieces evenly over the top of the batter.

8. Bake the cake in the preheated oven for 30 minutes, or until it is almost set.

9. While the cake is baking, prepare the Tuscan topping by melting the butter in a saucepan over medium heat.

10. Add the sugar, syrup, flour, and milk to the saucepan and bring the mixture to a boil.

11. Remove the saucepan from the heat and stir in the almond.

12. Spread the Tuscan topping evenly over the cake and return it to the oven for an additional 10-15 minutes, or until the top is golden brown.