If we are speaking in meta-ethical terms and not colloquially, then it makes no sense to ask what makes God good. He is the standard by which everything else is judged. He cannot be judged at all.
If you cannot judge something, then you know nothing about it. This is not to use the word judging in the sense of sentencing or condemning, but simply in the sense of forming an opinion about something - as in, "I judge her to be a good person."
The problem is, you have formed an opinion about God. Your opinion is that He is the foundation of all morality. Yet your definition of morality is "in accordance with God's character."
This means that when you say God is being moral, you are saying nothing more than "God is acting in accordance with His nature." Which tells us nothing at all, as it is a tautology. I'm afraid that, far from having left Euthyphro's Dilemma behind, you are still firmly stuck on it. Saying that God's character determine what good is means that whatever God's character was would be good. If God's character were what we call evil, it would be good. What would you do, say "God wouldn't be evil?" But how could you do that if you lacked an external standard to measure goodness by?
We can understand this by way of analogy. Everyone has in mind an absolute standard when making moral judgments. It’s necessary in order to make moral judgments. An absolute standard is one that cannot be evaluated at a higher level.
Sure. But the problem is, your standard is tautological. It is saying that "God's character is God's character," and therefore cannot be used to make a judgement of any kind at all. As a measuring stick, it is useless.
It's like a blank ruler on which is written, "This ruler can be used to measure (unidentifiable unit). The length of an (unidentifiable unit) is 1 (unidentifiable unit) long."
For some, the absolute standard is something like “human well being.” If this is the standard, then a question like: “how do we know that human well being is good?” doesn’t make any sense to ask. “Human well being” is the standard by which we measure everything else. It cannot itself be judged. So it is with my view on God’s nature.
But this doesn't help you. You're the one who claimed that you could answer Euthyphro's Dilemma. Counter-claiming that others do not have a reliable foundation for their morality either doesn't help your case.
(I do have a reliable basis for my morality, as it happens, but I'd like to stay on topic).