When making dense fruit cakes such as a Christmas cake, the batter needs to be heavy enough for the dried fruit and nuts to be suspended in it; if it's too thin the fruit will sink to the bottom.
Other seasonal fruit could be substituted for the rhubarb ... Preheat the oven to 180C/350F/Gas 4. Line 12 muffin tins with paper cases. In a large bowl, mix together the oil, brown sugar, egg ...