Start by heating the oil in a pan over medium low heat. Thinly slice an onion, and saute the onion in the oil with the Italian seasoning over low heat.
Bring a pot of water with one tsp of salt to a boil, and pasta and stir occasionally so that the pasta stick together.
Once the onions are cooked through, add the dried tomatoes, remaining salt, pepper, and garlic. Stir to evenly coat the vegetables in the seasonings, and warm through.
When the pasta is cooked, drain it remembering to reserve 2 cups of pasta water.
Add the yogurt or sour cream and 1 cup pasta water. The amount of sour cream or yogurt you add will determine how creamy your sauce will be. 1 cup for a milder less creamy pasta and a 2cups for a richer more saucy pasta. When adding pasta water I start with 1 cup then add more after I mix in the pasta if it needs.
bring the sauce mixture to a boil to help it thicken then remove from heat when it thickens.
Add the pasta and stir, adding any additional pasta water if desired.