In genetics a dominant trait is represented with a capital letter. And the recessive trait always with lowercase. When we are talking about a specimen being homozygous, it means that it has both equal alleles (AA or aa). And if you talk about it being heterozygous, the two alleles are different (Aa).
In this case the dominant allele would be "A".
And since it is homozygous, it corresponds to both alleles being equal (AA).