Heat a large skillet over medium heat, add olive oil and onion, saute until translucent, ~3-4 minutes. Add garlic and saute ~1 minute. Lower heat to low then add cream cheese, yogurt, zest, and lemon juice, whisking and adding pasta water a little at a time to create a sauce with a consistency that you prefer (more water will create a thinner sauce, you may not use all the reserved pasta water) and heat gently. Mix in dill, salt, and pepper.