Given that people can hallucinate/make up false memories, you sure you ate a grapefruit for breakfast?

So sure that regardless of what evidence you are presented, you'd be certain that you ate a grapefruit. Even if:

- I showed you videoproof that you were eating a sandwich for breakfast

- we had all of your family say they were having breakfast with you and saw you eating a sandwich

- a doctor came and said "I analyzed your stool and found no evidence of grapefruit"

- we had a message, cryptographically signed by a key you generated/controlled, that said "man this sandwich is delicious"

Even with any amount of evidence to the contrary, you'd still believe that you ate a grapefruit?

If not, then are you sure that it's fact that you ate a grapefruit, or it's just that all current evidence points to you eating a grapefruit?