Carefully remove any large seed from the lemon slices. Add the water and sugar to a saucepan over medium-high heat and bring to a boil, whisking until the sugar dissolves. Once boiling, add the lemon slices and reduce the heat to medium low or just until it’s simmering. Cover the pan with a piece of parchment paper and simmer until the lemon peels are translucent, about 30 minutes. Remove the pan from the heat and allow the slices to cool completely in the syrup. Once cooled, transfer them to a wire rack and allow to dry completely. You can save the syrup and store it in the fridge.
In a bowl, stir together the bread crumbs, garlic powder and pepper flakes. To make the goat cheese, heat a skillet over medium heat and add olive oil. Dip each goat cheese slice in the beaten egg then into the breadcrumb mixture, pressing gently to adhere. Place the goat cheese in the hot oil and cook until golden on both sides but not melted, about 1 minute per side. Carefully remove and set aside.
Assemble the salad by tossing the greens with some dressing. Add in the tomatoes and walnuts, tossing once more. Place the candied lemon slices and goat cheese on top. Serve with extra dressing if desired.