Welcome to ATP!
Assuming you're in the Northern hemisphere, you probably have fall frosts coming soon, or already present.
So things that become edible very quickly, AND are cold hardy, would seem to be your only chances, unless you have a good tight greenhouse or plastic film hoop tunnel or cold frame.
Even with those, short daylength might prevent many vegetables from producing until spring, even if they do germinate and survive.
Being a new gardener, I would urge you to at least consider leaving the harder gardening challenges for future years. What you're suggesting is classic hard-core gardener behavior called "pushing the zone", where we WANT to grow something where and when we WANT to ... not when the plant wants to grow. Gardening is always easier when you can give plants everything they need - in this case, long daylength and warmth or at least no-frost.
It may be too late for you to get in a good crop this winter. Greene's suggestion about "Goodies" | "Planting Calendar" is smart. Also, no one can give any good advice until they know your location, and first frost date, and how variable your fall weather is.
A few things like garlic and onions are happy planting shortly before frost because they grow a little in the winter and are all ready to shoot up in early spring. Some seed varieties will advertise "may overwinter with some cover". But those are usually cold-tolerant variety-by-variety, and be hard to generalize about.
It MAY still be possible to produce SOMEthing edible this winter, but you might put three years worth of work into it and get very little reward. Spending that energy instead on planning NEXT year's fall crops and hoop tunnels would get you more reward. Just no fresh greens THIS winter!
The key thing is to estimate "days to maturity" from the seed packet plus research, plus estimating the difference between seed-packet-optimistic "days to maturity" (which usually assumes perfect weather and ideal soil), and ACTUAL "days to maturity" , reflecting your actual temperatures, daylength, soil, and water availability.
When you know realistic "days to maturity" and YOUR average first frost date, you can count backwards from the estimated frost date and know when to transplant out or direct sow. For transplants, look up around how long it takes to germinate and grow to 2-4 inches - add that to "days to maturity" and know the latest date you can start seeds and reasonably hope for a crop before frost.
The first few years, give yourself a few weeks or a month extra, to allow for variables you learn as you gain experience. Consider TWO sowing of anything you really like, so that one of them is likely to be closer to the best date.
Realistically, plant something for fall as soon as the prior "summer" crop in that area has been harvested, if your summers are cool enough to do that. Record the date you sowed it. record the date you could harvest anything from it, and record the date it was really ready for harvest.
Now figure out how many weeks remain of weather that would be good for that crop (say, 3 more weeks).
Now you know that, next year, you could sow that fall crop as late as 3 weeks later than you did this year. Since weather might vary by more than 3 weeks, you would r4cord a RANGE of times to sow that crop for fall. The early dates will get you some results even if frosts come early next year. The later sowing will get you something even if a late heat wave kills or stunts your earliest sowing.
However - if you're looking for a challenge and have time and energy to spare this winter ... it is a time-honored gardening custom to attempt "the impossible" and prove it to be merely "very difficult".
Does anything become edible faster than salad greens?
Most lettuce varieties are cool weather crops, and so are most Brassica greens.
Some B. rapa varieties are VERY cold-tolerant. Like Tyfon / Holland Greens. Bland but very cold-hardy.
If you can get them to germinate and grow a little before days get very short, and they have enough weather protection to avoid frost, they will probably survive until spring. But between now and then you might not get rapid growth unless you have a lighted, heated greenhouse.
In mild-winter areas, you might get some growth and eat that winter growth using "cut-and-come-again" harvesting. Then let it regrow. Even if some frost hits, you can wait for it to recover and grow back.
If you had started leafy crops a month or two before first frost, and some were very cold-hardy like Tatsoi or Tyfon, they would have kept growing through mild frosts and even some freezes. But it might be too late for your area to start seeds outside this late.
