Chop the rhubarb into circa 3-5 cm long, finger-thick pieces. Large rhubarb stalks may benefit from peeling first. Mix the chopped rhubarb with the granulated sweetener. Let it sit for 30 minutes to macerate. This process draws out excess liquid and prevents the cake from becoming soggy.
Preheat the oven to 180 C / 350F and line the bottom of a 20 cm / 8 inch round springform with parchment paper. Grease the sides with butter.
In a large bowl using an electric mixer or in a food processor, beat the room temperature eggs until pale, fluffy and double in size. About 2 minutes.
Add the granulated sweetener, melted and cooled butter, cream cheese, almond milk, vanilla extract and almond extract (if using). Continue beating for another 1 minute.
Mix the almond flour, coconut flour and baking powder in a separate bowl. Then add to the wet ingredients and blend until you have a smooth batter.
Mix all ingredients in a separate bowl using a fork.
Fill the cake batter into the springform. Arrange the rhubarb pieces in a single layer over it. Top off with the streusel mix.
Bake in the preheated oven on the middle shelf for 60-65 minutes or until a skewer inserted comes out free of dough. Check after 35-40 minutes. If the top of the cake has browned sufficiently, loosely cover it with a piece of aluminium foil to prevent burning.
Let the cake cool completely before releasing and removing the springform.
