Homemade bread and homemade soup - any kind. These two smells are the most welcoming I can think of - when friends and family come to dinner in cold weather, walking into the house with these smells is an instant visceral welcome.
For breakfast, oatmeal with raisins or dates. I cook mine in an old crockpot (very low power, about 75 Watt) and it's so creamy by morning.