Resting metabolic rate does vary through the day: https://www.cell.com/current-biology/fulltext/S0960-9822(18)31334-4
However, this isn’t “burning fat”. Burning fat basically requires a sustained caloric deficit over a number of weeks or months. The general recommendation is a deficit of 500 calories per day.
The hard part is calculating intake and expenditure, and sticking to a course of a modest calorie restriction.
There’s no special time of day for more fat burning.