In a small bowl, mix the first 8 ingredients to make the ranch dressing. Scoop the insides of the avocado onto a cutting board and cube into 1-inch pieces. Transfer the cubed avocado to the bowl of a food processor with the lemon juice (optional) and process until creamy. Add the prepared ranch dressing to the food processor bowl and pulse until the mixture is fully blended. Transfer to a re-sealable container and chill until ready to use.