1. An oven comprising:a cooking chamber configured to receive a food product;
a radio frequency (RF) heating system configured to provide RF energy into the cooking chamber; and
an energy conversion assembly provided as a cooking surface of the oven, the energy conversion assembly being configured to convert at least some of the RF energy into thermal energy for heating the food product, while at least some other portion of the RF energy is directly applied to the food product to heat the food product,
wherein the energy conversion assembly comprising a base matrix formed substantially to have a plate shape and ferromagnetic particulate material dispersed in the base matrix,
wherein the ferromagnetic particulate material absorbs RF energy to transform the RF energy into thermal energy, and
wherein the energy conversion assembly comprises a first heat zone forming a first flat surface at a first portion of the energy conversion assembly and having a first concentration of the ferromagnetic particulate material therein, and a second heat zone forming a second flat surface at a second portion of the energy conversion assembly and having a second concentration of the ferromagnetic particulate material therein, the first and second concentrations being different from each other.