Step 1

Preheat oven to 180˚C/160˚C fan-forced. Brush a 25cm x 7.5cm x 7.5cm deep straight-sided loaf pan with butter or oil to grease. Line base and the two long sides with baking paper, allowing ends to overhang pan edges.

Step 2

Use an electric beater to beat together the melted butter, egg yolks, xylitol, sour cream and lemon zest in a medium bowl until smooth.

Step 3

Sift arrowroot and baking powder together over egg mixture. Add chia seeds and stir until combined.

Step 4

Thoroughly clean your electric beater, then whisk egg whites in a clean bowl until soft peaks form. Use a large metal spoon to fold a quarter of the egg whites into the seed mixture to loosen the mix. Gently fold in remaining egg whites.

Step 5

Spoon mixture into prepared pan and bake for 10 minutes. Reduce heat to 150˚C/130˚C fan-forced and bake for 45 minutes or until a skewer inserted into the centre comes out clean.

Step 6

Stand in pan for 15 minutes then turn onto a wire rack to finish cooling.