Rinse trout and pat dry. Sprinkle with lemon juice. Clean and wash spring onions and cut into rings. Season trout inside and outside with salt and pepper. Fill with spring onions.
Place in fish grill baskets with rosemary and lemon slices. Grill each side for about 8 minutes. Clean and wash the tomatoes. Carve crosswise. Drizzle with oil, season with salt and pepper. Sprinkle with herbs.
Wrap loosely in slightly oiled aluminium foil and grill briefly.