To prepare a summer feta burger with gourmet cheese spread recipe, first you need to prepare the ingredients. First, you'll need the following ingredients: 2 tbsp. kosher salt, 14 cup (60 ml) olive oil, and 1 tablespoon (2.5 g) chopped scallions. To make the ketchup, mix together 2 tablespoons (120 milliliters) Greek yogurt with 2 teaspoons (1.25 fl oz) lemon juice. Then, add the grated Parmesan cheese to the yogurt mixture and mix until the cheese is fully melted. Pour the mixture into the buns and bake for 12 to 15 minutes or until they are golden brown. Remove from the oven and allow to cool for 5 minutes before serving.