Preheat oven to 170°C. Lightly grease a 6-hole Texas muffin tray with butter or line with muffin wrap papers and set aside.
Place spinach into mixing bowl and chop 5 sec/speed 5. Transfer into a bowl and set aside.
Place tomatoes into mixing bowl and chop 5 sec/speed 7. Transfer into bowl with spinach and set aside.
Place butter into mixing bowl and melt 1 min/100°C/speed 3.
Add yoghurt, eggs, oil and water and mix 10 sec/speed 3.
Add flours, baking powder, bicarbonate of soda, salt and pepper and mix 5 sec/speed 4, or until combined.
Scrape down sides of mixing bowl with spatula. Add feta and reserved spinach mixture and combine 20 sec//speed , or until incorporated. Spoon mixture evenly into prepared muffin tray.
Bake for 20-25 minutes (170°C), until muffins are golden brown or until a wooden skewer inserted into the centre of the muffin comes out clean. Serve warm.
Tip: To make your own rice and/or buckwheat flour, place 250 g rice into mixing bowl and mill 2 min/speed 10. Use as needed.
Danish feta has a smoother, creamier texture than Greek or Australian feta.
These muffins are best eaten on the day they are made. They are also an excellent lunchbox idea.