Add the lemon juice, tomato juice, honey, roasted garlic and dried sumac to a blender and blend for about 15 seconds and then slowly add the oil to emulsify (This can also be done in a bowl with a whisk if need be)
Check for seasoning and add salt and pepper to taste. Reserve in the chiller until needed.
To assemble:
First place the Labneh down in an even layer on a large plate. Gently dress the tomatoes with the Sumac Vinaigrette and then place them on top of the Labneh. Place the avocado slices between the tomatoes. Then garnish the tomatoes with the red onion slices, radish slices, basil leaves and sumac. Drizzle a desired amount of tomato vinaigrette on the salad and finish with sea salt.