Stir together flour, sugar, baking powder, baking soda and salt in a mixing bowl. Add raisins (or currants), tossing to coat. Melt butter in a small saucepan over low heat. Cook, swirling the pan, until it turns a nutty brown, about 1 minute. Transfer the butter to a bowl. Add oil, 1 cup yogurt, egg and orange zest and whisk until blended. Add the yogurt mixture to the dry ingredients, stirring just until combined (the dough will be sticky).