In my experience, all citrus seedling that I germinated started with a little stem with no visible presence of leaves, than the first 2 leaves slowly developed at the tip of the little stem and so on.
I recently germinated a seedling that came up from the dirth with the first 2 leaves almost completely formed. I wasn't even sure it was a citrus seedling, but based on the smell of the leaves I no longer have any doubts.
In your experience have someone of you guys ever seen something like that?

That is normal. The first two leaves to develop are small rounded leaves. After that the plant will start to produce normal leaves.

http://informedfarmers.com/citrus-stage-i-seedling-management/

Ivannn, can you post a picture?

Laaz, the picture in your link shows the cotyledons (seed leaves), along with a shoot that has the first true leaves forming at the tip. I think that's what Ivannn normally sees, maybe with the cotyledons below the soil surface if the seeds were planted deeper. Ivannn, did you mean cotyledons or that this plant's first true leaves started out already formed in the seed such that they open right out? If so, I've never seen that before in citrus, but I do see it in other plants like beans.

Also, I noticed your up to 3 n's in Ivan, Ivannn...has it always been that long, or are you adding n's?

Actually there something that's not very typical in this seedling. The thing is more noticeable now than in the pic I posted, the 2 first leaves are not at the same height on the stem, one is more or less 1cm above the other.

Ivan is that concrete you are growing in?

Ivannn, is that wood ash spread on the soil surface? If so, do you use it to deter pests?

It's just an effect of the picture, maybe the dirt was a little dry