1.Preheat oven to 180°C. Grease a 10cm x 20cm loaf pan (top measurement); line base and long sides with baking paper, extending the paper 5cm (2in) over the edge.
2.Heat oil in a medium frying pan over medium heat; cook onion, garlic and chopped rosemary, stirring, for 4 minutes or until light golden. Transfer to a large bowl; cool slightly.
3.Squeeze excess liquid from zucchini. Add zucchini to onion mixture with sweet potato, flour, parmesan, nutmeg and pepper; stir to combine. Make a well in the centre, add egg, buttermilk and sun-dried tomatoes; stir until just combined. Spread mixture into pan; level surface, then top with rosemary sprigs.
4.Bake loaf for 1 hour or until browned and a skewer inserted into the centre comes out clean. Cover loosely with foil if overbrowning during cooking. Cool in pan for 20 minutes before turning out. Serve warm or at room temperature.
If you don’t have any buttermilk on hand, you can make your own: combine ½ cup (125ml) low-fat milk with 2 teaspoons lemon juice in a small jug.
Spread with butter or herb-flavoured soft cheese or goat’s cheese.