Remove the stems and seeds from the dried chiles. Place the chiles in a pot with the garlic, onion, and tomato. Cover with water and bring to a boil. Simmer for 10 minutes until the chiles are soft.
Transfer the chiles and vegetables to a blender. Add the chicken broth and salt. Blend until completely smooth. Strain the sauce through a fine-mesh sieve into a bowl to remove any solids. Set aside.
In a large skillet, heat enough vegetable oil to cover the bottom to about a centimeter deep. Fry the tortilla triangles in batches until they are golden and crispy. Remove with a slotted spoon and place on a paper towel-lined plate to drain. Season with a pinch of salt.
Pour the prepared red sauce into a clean skillet and bring to a simmer. Add the fried tortilla chips and gently stir to coat, cooking for just 1-2 minutes until they are slightly softened but not mushy.
Serve the chilaquiles immediately on a plate, topped with crumbled cheese, a drizzle of sour cream, and diced onion. Add any other optional toppings you desire.