In a small mason jar, stir together milk and lemon juice. Let sit for 5 to 10 minutes; it may curdle and smell sour. Mix together sour cream and spices until thoroughly combined.
Add sour cream mixture and oil to a mason jar, and stir until smooth. Let sit in the fridge for 1 to 2 hours to thicken.
If you use the ranch dressing to dip veggies, you can leave the oil and milk for a thicker version.