Rhubarb and Ginger Polenta Cake

Gluten-free & Dairy-free

This is a recipe I've been using for years - two layers of shortcake-style dough enclosing some fresh fruit. I usually make it with butter and SR flour, but wanted to see whether the recipe worked if it was made both gluten- and dairy-free. I decided to use polenta in place of 1/3 of the flour, as in this Nigel Slater recipe, a commercial brand of gluten-free flour and a non-dairy spread instead of butter.

This recipe works well with any type of fresh fruit filling, but something like rhubarb, which releases a lot of liquid during cooking, needs to be cooked first, then drained. I roasted 500g of rhubarb (the first of the season, incidently), cut into 4cm lengths, with about 50g of sugar; you might need more sugar if you don't like really sharp fruit.

Ingredients
150g caster sugar
150g non-dairy spread, suitable for baking
100g polenta (I only had the instant kind)
200g gluten-free plain flour
1 teaspoon baking powder
1/2 teaspoon xanthan gum
1/2 teaspoon ground ginger
1 large egg
500g sweetened cooked rhubarb, drained of cooking juices
3 balls of stem ginger, finely chopped

Method
My usual method is to melt the butter, then stir in the sugar and egg, then lastly add the flour, but I didn't think this would work as well with the non-dairy spread. Instead I followed the method in Nigel's recipe, which is to put all the dry ingredients into a bowl, rub in the fat, then mix to a sticky dough with the egg. The gluten-free flour and polenta made a much stickier dough than usual, which was almost too soft to work with - next time I think I'll add another 25g of flour.

Pre-heat the oven to 180C.
Once mixed, 2/3 of the dough is spread over the base of a 20cm springform tin, which has been greased and base-lined with baking parchment. The dough needs to be worked up the sides of the tin to make a wall about 2cm high.
Spread the fruit onto the base, packing it closely together but leaving the 'wall' uncovered.
Sprinkle the chopped stem ginger over the rhubarb, then drop the remaining dough on top of the the fruit in small teaspoonsful, starting at the edges and working inwards. Use the spoon to flatten and spread the dough as much as possible, but it isn't necessary to completely cover the fruit.
(The method of assembling the cake is covered in more detail, and with photographs, in this post.)
Bake for about 55 minutes until the cake is golden and feels solid. Cool in the tin.
The cake can be served warm but this gluten-free version is quite fragile, so I'd recommend serving at room temperature.

If liked, the top can be sprinkled with flaked almonds or demerara sugar before baking, or the cooled cake can be dusted with icing sugar before serving. As I mentioned earlier, almost any fruit can be used as a filling - sliced apples and a handful of sultanas, for instance, or sliced plums - and complimentary spices can be used in the dough, rather than ginger.

Rhubarb and ginger is a classic combination which worked well in this cake. There was just a hint of ginger in the cake dough, but the stem ginger in the filling was more pronounced and added an extra texture too, along with the graininess of the polenta. This cake was softer and more fragile than the same cake made with the usual ingredients, but I was pleased with how well the 'conversion' to a gluten- and dairy-free version turned out.