In medium bowl, combine flour, cinnamon, cardamom and salt.
In large bowl, whisk together eggs, sugar, butter and vanilla. Stir in carrot and apple. Stir in flour mixture, alternating with yogurt until batter is smooth. Spoon into large zip-lock plastic bag and press out excess air. Cut small corner off bag; gently press to pipe dough into greased doughnut pan, filling 10 doughnut cavities.
Bake in 425°F (220°C) oven for 18 to 20 minutes or until lightly browned and doughnuts spring back when lightly touched. Let cool in pan on rack for 5 minutes; invert onto rack and cool completely.
Maple Glaze: In small bowl, stir together icing sugar, maple syrup, vanilla and cinnamon. If necessary, add water to thin icing to desired consistency. Drizzle doughnuts with glaze when cooled.
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