Answer

If by atham you mean a Jain fasting day / aatham-ashtami observance, then the main rule is:

• For the person observing the fast: no food is prepared for eating.
• For the rest of the family: prepare simple Jain satvik food according to your tradition.

Explanation

Usually, Jain food on such a day should be:

• Fresh and simple
• Without root vegetables like potato, onion, garlic, carrot, radish, beetroot, etc., if you follow strict Jain cooking
• Without fermented items
• Without excessive oil, spice, or fried food
• Made with respect for ahimsa and purity

Common simple options may include:

• Roti, plain rice
• Dal or variyali-style light dal
• Simple shaak made with non-root vegetables
• Khichdi
• Fruit, if your observance allows it

Spiritual Understanding

The purpose of atham observance is not only to avoid certain foods, but to practice:

• Self-discipline
• Non-violence
• Purity of mind and body
• Detachment from taste and enjoyment

So the food should remain light, respectful, and in harmony with Jain principles.

Takeaway

If you want, I can also give you a simple Jain aatham menu for upvas, ekasan, or biyasan.