Jeden Abend zünde ich eine Kerze an.

• Abend is a masculine noun (der Abend).
• Time expressions answering “when?” often take the accusative in German (the so-called temporal accusative).
• The determiner jeder (every) changes to jeden in the masculine accusative.

• Jeder is the masculine nominative form (“every evening” as subject).
• Here Abend isn’t the subject but a time expression in the accusative, so jeder → jeden.

• anzünden is a separable-prefix verb.
• In main clauses, the prefix (an) detaches and moves to the end of the clause.
• The conjugated stem (zünde) occupies the second position.

• Eine Kerze is the direct object of anzünden.
• Transitive verbs that act upon someone or something take a direct object in the accusative.

Yes. Both orders are correct:
– Jeden Abend zünde ich eine Kerze an. (time first → verb–subject inversion)
– Ich zünde jeden Abend eine Kerze an. (standard Subject–Verb–Object order)

• Jeden Abend = “every single evening” (stresses each individual evening).
• Abends = “in the evenings” (general, habitual).
• Am Abend = “in the evening” (refers to the evening time period, can be singular or habitual with context).

• zünden (without prefix) can mean “to ignite,” often used for fireworks or explosives.
• anzünden (with prefix) specifically means “to light” things like candles, fires or stoves.
• For lighting a candle, anzünden is the usual choice.

• German is not a pro-drop language—you normally include the subject pronoun.
• Omitting ich would sound incomplete or poetic; in standard speech/writing, keep ich.