Preheat the oven to 350 degrees F. Butter an 8x8 baking dish.
Place drained, canned sweet potatoes in a large bowl.
Using a potato masher or a fork, beat in white sugar, cinnamon, melted butter, evaporated milk, eggs, and vanilla until well combined.
Spread sweet potato mixture evenly into the dish. Bake for 40 minutes.
When the casserole nears the end of its baking time, make the topping. In a medium bowl, using a fork, mix the pecans, brown sugar, flour, and melted butter until just combined and crumbly.
When the 40 minutes is up, remove the casserole from the oven and sprinkle the topping evenly over the sweet potato mixture. Bake for an additional 20-25 minutes or until the top is golden brown.
Remove the casserole from the oven, cool, and enjoy!