Rub cut side of garlic on both sides of bread. Toast the bread. Butter each slice. Set aside.
Grate the remaining garlic into a small bowl and stir in mayo, tomato paste, lemon juice, and ⅛ tsp salt. Set aside.
Heat oil in a large nonstick skillet over medium-high heat. Add turkey sausage and cook, breaking up large pieces with a wooden spoon, until almost cooked, about 3 minutes. Add spinach, scallions, water and ⅛ tsp. salt; cook, stirring occasionally, until the sausage is cooked through and the spinach is wilted, about 2 more minutes. Transfer to a serving platter or divide among 4 plates.
Crack eggs into the pan and sprinkle with the remaining pinch of salt and pepper. Cook for 1 minute. Cover and cook until the whites are just set, about 1 minute more. Top the spinach with the eggs and serve with the aioli and the toast.