Prepare the Yogurt Spread : In a small mixing bowl, combine the Greek yogurt and fresh lime zest. Stir until the mixture is uniform and fully incorporated. Set this tangy base aside while you prepare the other components.
Slice the Avocado : Halve the avocados and carefully remove the pits. Peel the skin from each half and place them cut-side down on your cutting board. Thinly slice each half lengthwise into elegant, ¼-inch-thick pieces.
Pan-Sear the Bread : Position the large cast-iron skillet over medium-high heat. Once hot, place the bread slices in the skillet. Toast for approximately 2 minutes per side, until each slice achieves a deep golden-brown color with slight char marks and feels crisp to the touch.
Assemble the Base : Transfer the pan-seared bread from the skillet to four individual serving plates. While the toast is still warm, spread a generous, even layer of the prepared lime-yogurt mixture over each slice, covering it from edge to edge.
Arrange the Topping : Gently lift the avocado slices and fan them out over the yogurt layer. Overlap the slices slightly to create an attractive pattern that completely covers the surface of the toast.
Final Garnish : For the finishing touch, drizzle the maple syrup evenly over the fanned avocado on each toast. Conclude with a light sprinkle of sumac and a pinch of red pepper flakes, if using, to add a hint of warmth and vibrant color. Serve immediately for the best texture and flavor.