When a person makes himself a meal, he says "treating myself with" but what can we say for when someone else makes you food?
The phrase that pops in my mind is cooked for me:
I went over to Tim's house and he cooked for me.
Some might argue that this won't work if the meal doesn't involve heat from a stove or an oven, as in the case of sandwiches or a garden salad. If so, you can just use the verb make:
We went over to Bob's house, and Melissa made us lunch.
We know we're in for a treat whenever Ed makes us sandwiches.
Another verb that can be used is fed:
They hosted a wonderful picnic and fed us hummus.
That's an interesting question: when we are talking about some special delicacy, I can treat myself, you can treat yourself, he can treat himself, but it sounds wrong to say that you are treating me.
The problem is that treat has multiple meanings. The verbal form "treat", meaning giving somebody a delicacy is only valid in a reflexive sense, for example "treat myself" or "treat yourself".
The expression "treat somebody to dinner" is similar, but this really means paying for a meal for somebody, rather than offering them a particular delicacy.
If you use "treat" without the "to", the meaning is completely different, for example
You have treated me badly.
It is possible to use "treat" in the situation you describe, but you would have to use the noun version:
This is a real treat for me!
[whatever it is] is a real treat for me!
If you want to put the emphasis on the person who is providing the treat, you could say
You are spoiling me!