This is a shameless attempt in stealing TA's thunder.
Checked Delivery Hero, and the varying discounts have been applied to participating restaurants. Last week they called it a "Melbourne Cup Special" but seems pretty standard for Tuesdays now. Browsed a few suburbs and the best I found was 40% unlike previous weeks at 50% - let me know if you find otherwise.
Participating Restaurants will have a code displayed in the restaurant name and cart. Enter the code on checkout to apply the discount and pay with Credit Card/Paypal. Discount code is only valid for first order from the restaurant. Look out for restaurants that have a red % symbol or filter for Deals. Click on the symbol to view discount.
If you're in Inner-east Melbourne. I can recommend Cuate who have 40% off. The nachos is big.
Don't forget an extra 5% Cashrewards too! ;)