reflexive used for emphasis

Question

Me comí el pastel

I think, I have seen statements like the above explained in 2 different ways.

One is to indicate - I ate it up And I think I have seen it as emphasizing that it was - I that ate it and not someone else

When used for emphasis - how do you know what it is trying to emphasize?

Thanks

Answer 1

Me comí el pastel.... I ate up the cake (nothing left).

Comí el pastel ... I ate the cake.

Comí el pastel yo / Yo comí el pastel ....... I (was the one who) ate the cake. (For this we also say "Yo fui el que comió el pastel").