I've done a lot a single ring camping cooking. My camper van has a bit more kitchen than yours but I still take a similar approach when staying in it and going to work. Here's a typical example that worked for me.
- I cooked a curry at home and put a portion in the fridge (freezing is also an option).
- When camping I boiled water and put it in a vacuum flask.
- Then I heated the curry in my larger of two pans, with a lid on but stirring frequently. Heating gently meant it didn't stick.
- Cooking the rice (using the recently boiled water, and an excess of it rather than measuring) took place in the smaller pan, using the larger as a lid to keep the sauce hot.
- Then I drained the rice water into a mug or similar, added the sauce to the rice, and poured the cooking water into the sauce pan with some washing up liquid so it could soak while I ate and would be easy to wash up. (I used mess things to cook in and eat from when in the tent, it's easier with a few more containers).
The same thing works with pasta. Noodles (ramen) cook much quicker than spaghetti, saving fuel, and make a perfectly acceptable substitute. The principle of keeping one thing hot over the top of the other is key, as is a vacuum flask. Washing up in starchy water doesn't work very well, but soaking and prewashing do, allowing you to wash up in a minimum of water.
If you don't want to rely on taking home made ready meals there are plenty of books and blogs devoted to one-ring recipes (recipe requests are off topic here anyway).
Pasta, rice and noodles all work quite well, needing no preparation. Frying can be a pain if you're cooking in the van - it makes things greasy and the smell lingers, but in dry weather it works outside (if you can take the stove out). A canned (jar/packet etc. ) sauce can be used with something like tinned tuna if you don't have fridge space. Defrosting in a cool bag can take 24 hours or more and it uses a lot of gas to defrost on the stove.