Wash potatoes and pierce several times with a skewer or fork. Microwave on HIGH for 8 - 10 minutes or until tender. Allow to stand for 5 minutes.
Cut the potatoes in half. Scoop out the cooked flesh into a bowl and mash.
Microwave the mushrooms on HIGH for 2 minutes. Mix mushrooms, capsicum, yoghurt and pesto into mashed potato.
Pile potato mixture back into potato skins. Smooth the top into a nice round shape. Place a slice of tomato on top and reheat in microwave for 6 minutes. Serve immediately.