Heat the oven to 200°C (400°F).
In a large mixing bowl, stir together the spelt flour, ground almonds, baking powder, ground cinnamon, ground ginger, salt and light brown sugar.
In a smaller mixing bowl or jug, lightly beat the eggs with the milk and oil. Add the wet ingredients to the dry ingredients and mix well with a wooden spoon or spatula until combined.
Finely grate the zest of the blood orange and add to the batter. Chop off each end of the orange and stand it on one end. Using a sharp knife, carefully remove the skin and pith from the orange. Dice the flesh of the orange, discarding any seeds. Finely chop the rhubarb into small dice and add it to the batter along with the orange. Stir until the fruit is evenly distributed.
Divide the batter between 14 muffin cases and bake for 25-30 minutes until puffed up and golden and a skewer inserted into the centre of the muffin comes out clean. Leave to cool.