Cut 12, 1/4"-1/2" slices from baguette . Keep the rest of the baguette for another use. Place on cooking sheet and bake for 15 minutes (keep an eye on them, as ovens bake at different rates. Don't let it burn!).
While bread is toasting, melt butter and stir in sugar. A good way to do this is by using a double broiler, but I just used the microwave.
Remove bread from oven and brush with butter/sugar mixture. Return to oven for another 10-15 minutes. If desired, sprinkle with additional sugar after removing from oven. Cool and eat.
Notes
I did a quick pass under the boiler to get a little more color. You can use more slices if you put less butter/sugar on each one. Adapted from cookpad.