Mix the ground flax and water in a small bowl or cup and set aside for 15 minutes until gelatinous (you can use 2 eggs in place of this and ignore this step)
Meanwhile preheat the oven to gas 4 / 180C / 350F and grease & line a 20cm cake tin
Make the topping first by mixing the flour, ground almonds and sugar together. Rub in the butter with your fingers until the mixture resembles crumbs. Set aside
For the cake, cream the butter and sugar together in a large bowl
Add the flax mixture and the milk (or 2 eggs), half of the ground almonds and stir in, then add the rest of the ground almonds and the extract and mix together
Add the baking powder and xanthan gum if using to the flour, then fold into the rest of the cake batter
Pour the cake batter into the tin and even it out with the back of a spoon
Spread the cherries over the top of the cake batter
Sprinkle the streusal topping over the cherries and add the flaked almonds on top of that if desired
Bake for 45 - 55 minutes or until the almonds / topping is slightly golden and a skewer inserted into the middle of the cake comes out clean
Let stand in the tin for 10 minutes before releasing. Dust with icing sugar if desired before serving
A lovely dessert served warm with custard or ice cream
