My child also has Autism. We planted a veggie garden that he cares for. Growing it himself has encouraged him to nibble on new veggies.

He prefers smooth textures and soft food. We blend a lot of veggies and add lots of lentils to foods like spaghetti bolognese.

We also found that smell really matters. We have found that foods that have a strong smell, he simply won't touch.

We've got him to help cook a lot of recipes and gradually added a little bit of a new food at a time until he is used to it with a dish he enjoys.

Hi so I agree with finding the right texture. You’d be able to narrow down if they like soft, or crunchy etc and try to start with that.
So my child loves meat. So I mix a lot with meat. But then some textures of meat they won’t touch so it’s working with what they like. Also my child loves crunchy so I partially steam carrots. I do this as they hate boiled and not so fussed on roasted but steaming lightly they eat. Could also try and put a little bit of honey on to start with to give a slightly sweet taste and slowly reduce the amt later on.
Also i find getting them involved in the cooking process helps sometimes. So could try and make a slightly healthy muffin or even unhealthy to start with to get them trying the texture out. And if they like them change up later. I find helping with cooking helps.

I definitely wish I knew. I found out our son is too. Which is why he is picky.. he only likes Pastas , fried chicken, roast beef, steaks he recently Started to love using ketchup with his fries.. so that was a little start.. he loves all fruits though. I make sure there’s a lot of apples in the house.

My son won't eat meat or chicken & a lot of veges due to texture, but loves any type of pasta. So I puree a lot of dishes (stir fries, casseroles, thai etc) & pour them over pasta topped with cheese (another favourite) I read about a young woman who only would eat a meat lovers pizza, but over a period of time, they were able to slowly add veges, so now she eats a more balanced one.

Sorry I don’t have first hand experience with ASD but do have a good friend with a child in the spectrum. I was recently reading an article about ASD and sensory eating. It was written by a lady who has autism and I found it really insightful. To summarise, it basically made a distinction between fussy eating and sensory eating. The author was saying that for her, different textures triggered a negative sensory experience so she preferred to eat a lot of highly processed foods due to the consistency in texture. She knew certain foods where not healthy for her and that she should be eating more fruits and veggies etc but she struggles with the texture of such foods. Her food choices were basically made in the texture of the food rather than the flavour.
I would try and determine what foods your child is willing to eat and try to stick with foods with similar textures. Try different cooking techniques to achieve the desired texture and see if you can sneak in a few new foods that way.
Also, for an average kid you need to offer a new food up to 20 times before they will try it. This number is much higher for kids on the spectrum, do keep offering a variety of foods even if they are being rejected at the moment.
I hope this information is helpful for you and that you can successfully expand your child’s menu.

Would an occupational therapist be able to help you as far a textures etc are concerned?