A fluid simulation is supposed to be creating a fluid mesh which can be rendered afterwards - this will be showing in renders using the material which is on the domain object. And if there is no material, it will show the default (almost) white surface.
If you do not want to display the fluid mesh (to show particles like in your example) you could disable Mesh in the domain settings - but then the complete bounding box of the domain will be shown with whatever material you put on it. But disabling it will save you simulation time if you really do not need the mesh.
So to get rid of the domain in render, you have to give it a material with a simple Transparent BSDF set to fully white, which makes it completely invisible for the camera.
Fluid domain with Mesh enabled and no (or default) material:
Fluid domain with Mesh disabled (no matter if it was simulated or not) shows domain's bounding box in render:
Fluid domain with a completely transparent (= invisible) material - no matter if Mesh is enabled or disabled: