In a bowl, whisk the eggs with the hot sauce and salt until blended.
Heat the olive oil and butter in a medium-sized pan (either well-seasoned cast iron or nonstick) over medium heat until it’s bubbling. Pour in the egg mixture and cook, stirring often, until the eggs are just set, about 1 to 3 minutes. Remove the pan from heat and transfer the egg mixture in a bowl.
In a separate, large pan, warm the tortilla over medium heat, flipping occasionally. Once the pan and tortilla are warm, sprinkle one-half of the feta over one-half of the tortilla. Top the cheese with the avocado, scrambled eggs, cherry tomatoes and the remaining feta. Sprinkle some coriander leaves.
Press the empty tortilla halve over the toppings. Let the tortilla cook until the bottom gets golden and crispy, about 1 to 2 minutes. Flip it and cook until the top side is golden and crispy.
Remove the pan from the heat and transfer the breakfast tortilla to a cutting board. Let it cool for a few minutes to give it time to set, then slice each quesadilla into 2 slices with a very sharp knife. Serve immediately, with your favorite salsa and/or hot sauce on the side.