Questions & Answers about Danas je ovaj desert jeftiniji od kolača.
Je is the present-tense form of biti (to be) for he/it (is). In Croatian it’s a clitic (a “weak” word) and normally goes in the second position of the clause (after the first chunk).
Here the first chunk is Danas (Today), so je comes right after it: Danas je ….
You can often move the first chunk, and je will still try to stay in second position: Ovaj desert je danas jeftiniji…
Usually, in standard Croatian, you do not omit je in the present tense when you have a predicate adjective like jeftiniji.
In very informal or headline-style language you might see omission, but for learners it’s safest to keep je: Danas je ovaj desert jeftiniji…