Heat the broiler and line a sheet pan with foil. Juice one whole lemon to get 3 tablespoons and set aside. Cut the remaining ½ lemon into 3 or 4 thin slices.
In a bowl, toss together the lemon slices, scallions and add 1 tablespoon olive oil. Place on sheet pan and broil until blackened about 7 to 9 minutes for the scallions and 5 minutes for the lemon slices. Transfer to cutting board to cool slightly.
In a food processor, add the Feta, cream cheese, remaining olive oil, reserved lemon juice, black pepper, cayenne and hot water. Puree until very smooth.
Take a few pieces of the scallions and chop, reserve for garnish.
Add the rest of the scallions to the food processor and pulse to combine, leaving some chunky pieces. Taste for lemon and adjust as needed.
Transfer to a bowl and garnish with lemon slices, chopped scallions, and black pepper cayenne.
Serve with pita chips or cracker/other chip of your choice.