Combine ham & onions. Place 1/3 cup into center of each tortilla. Top with 2 tablespoons of cheese. Roll and place tortilla seam side down into greased 9x13 pan.
In a bowl, combine flour, cream, eggs and salt (if desired) until smooth. Pour Over tortillas. Cover and refrigerate overnight (8 hours).
Remove from refrigerator 30 minutes before baking. Cover and bake at 350 for 25 minutes.
Uncover and bake for 10 additional minutes.
Sprinkle remaining cheese over the top and bake for 3 more minutes or until cheese is melted.
Remove from oven and let rest 10 minutes before serving.