Preheat oven to 170ºC fan forced and arrange oven rack to middle of oven.
Grease and line large loaf tin (10cm x 30cm) or round 24cm cake tin with baking paper.
Place rind, sugar and butter into TM bowl and chop 10 sec/speed 5. Scrape down sides of bowl and repeat.
Insert Butterfly and mix 1 min/speed 4, scraping down sides of bowl after 30 seconds.
Add eggs and mix 20 sec/speed 4, scrape down sides of bowl and mix 5 sec/speed 4.
Add flour, custard powder, yoghurt and lemon juice and mix 15 sec/speed 3. Scrape down sides of bowl and mix 15 sec/speed 3.
Pour batter into cake tin and smooth top.
Bake 50 minutes for a cake tin or 1 hour for a loaf tin, adding 5-10 minutes more if necessary (test with a skewer).
Cool in tin 15 minutes then turn out onto cake rack to cool.
Serve dusted with icing sugar, or with a drizzle of lemon icing.