I concur with the suggestions that have already been made. Putting on my chemist hat to reply to this... (Sorry that it's so long, I'll include a short/simple suggestion at the end, and a couple of recipes.)
There are three types of dietary iron: heme-iron which comes from animal blood, organic non-heme iron which comes from plants, and mineral iron which comes from cookware.
The heme-iron is most easily absorbed by the body, and is generally more concentrated.
Plant based and mineral iron are more readily absorbed if they are eaten with foods that are high in organic acids such as fruits, vinegar, or lacto-fermented veggies, or with sulfur compounds such as those contained in onions and garlic.
Mineral iron comes from rusty knives, cast iron, etc, and can contribute significant iron to a diet.
To get the most iron out of a cast iron pot, the pot shouldn't be seasoned, because a layer of varnish interferes with the absorption of iron. Also, acidic foods that are in contact with the pan for extended periods extract more iron: Something like a tomato soup that boils all day. Or a barbecue sauce over meat. Or a stir-fry with not-red cooking-wine or vinegar added to the sauce. Or a pot of beans with vinegar added to the cooking liquid. The taste of boiled beans seems better to me if vinegar is added to the cooking water. Too much iron in food can make it taste metallic, so calibrate your taste buds, recipes, and cooking methods with the pans you are using.
Tannins and other polyphenols, like found in
coffee, tea, and red-wine, interfere with absorption of plant-based iron, so consider skipping coffee, tea, and red-wine for a few hours before/after a high-iron meal. Other foods high in polyphenols include walnuts, almonds, some legumes, red wine, cinnamon, cloves, chocolate. Basically, things that taste astringent.
Phylates, like found in legumes and other seeds, may interfere with absorption of plant-based iron. Phylates can be reduced by soaking prior to cooking. I highly recommend soaking beans anyway for increased flavor. Soaking, sprouting, and fermenting all reduce phylate concentrations.
Medications such as proton-pump inhibitors or antacids can reduce the absorption of iron.
Calcium inhibits the absorption of iron. So it may be helpful to avoid high calcium foods in combination with a high-iron meal. High calcium foods include dairy, and fish canned with bones. For example, tuna (no bones) would be a better choice than bony sardines.
A little bit of animal-based iron added to a meal increases the absorption of plant-based iron. Thus we get back to traditional ways of eating such as soups or stir-fry.
Beta carotene with a meal increases the uptake of organic iron. Foods high in beta carotene are orange or dark green: squash, parsley, cilantro, bok-choi leaves, broccoli, etc...
Oxalates severely interfere with the absorption of iron. (So while spinach is a high-iron food, it doesn't contribute that iron to the body.) That might go a long way towards explaining why I really dislike the taste of oxalates in my food. High oxalate foods include spinach, Swiss chard, rhubarb, beets, coffee, black tea, chocolate, nuts. They only interfere while they are being digested. Broccoli, and bok choi are low in oxalates.
A protein in eggs interferes with absorption of iron.
My suggestion would be to eat one high iron meal per day... And don't eat anything else for two hours before or after that meal. Liver and onions is the most traditional high-iron meal. The sulfur compounds in the onions help with absorption of the iron. Cooking it in an unseasoned cast iron skillet and adding an acid such as not-red cooking wine, tomatoes, or vinegar would help. Adding some high carotene greens like parsley, broccoli, or cilantro would help. Adding onions or garlic would help.
A high iron meal might consist of parsley/onion/tomato soup cooked in a cast iron pot. Or a parsley/onion/vinegar stir-fry cooked in a traditional iron wok. Or fried liver/onions simmered with tomato sauce and onions in a cast iron frying pan.
Here's a chart from a nutrition program I use that suggests quantities of (single item) food required to meet the adult female RDA.
See also:
Do You Absorb More Iron Cooking in a Cast Iron Pan? For what it's worth, I do most of my cooking in cast iron.
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