Crepes with Chicken and Potato

Name: Crepes with Chicken and Potato
Ingredients: 12 Savory Crepes; 2 Tbsp unsalted butter; 2 white onion (quartered and sliced thin); 1 tsp granulated sugar; 1 lb chicken tenderloins (or chicken breast cut into strips); 3 lemons (quartered); 1 Russet potato (peeled and ½-inch dice); 6 oz Gruyère cheese (shredded); 2 pinches kosher salt; 1 pinch fresh cracked pepper; 2 Tbsp all-purpose flour; 1 ½ cups milk; ½ tsp kosher salt; 1 Tbsp fresh lemon juice; zest of half a lemon; ¼ cup chopped chives; 1 large tomato (diced)